Eating and Evolution: Are Prey Preferences Causing the Evolution of Killer Whales?

When I was an undergrad, a lowly freshman who just knew she wanted to study biology, I took an internship at SeaWorld Orlando. I was excited that I got to participate in a real research project doing actual sciency stuff. The project was on the nursing behaviors of captive baby killer whales. Really cool right? Little did I know that actual science is composed of hours upon hours of tedious observation and documentation (2:00pm – melon bumping, 3:00pm – melon bumping, 4:00pm – melon bumping…). Despite that (or, who knows, maybe because of it), it was an neat project that boosted my interest research biology. And I got to watch killer whales for hours every week. So when I came across the paper for today’s post it really reminded me those times.

A new study published in the Proceedings of the Royal Society B, Biological Sciences looks at niche variation within sympatric killer whale populations in the North Sea. Those of you familiar with the terminology I just used might want to skip to the next paragraph. Otherwise, let’s hit a few terms first. We’ll start with the niche variation hypothesis. In the simplest terms, a niche describes where a species lives and the roles it plays in its habitat. The niche variation hypothesis describes differences within a species that are correlated with the variety of foods and habitats that are used by various populations. For example, why do island birds of the same species have different bill sizes? Likely because their bills adapt to the food items they are exploiting on their own island. It conveys a competitive advantage which results in a reproductive advantage that will lead, eventually, to an evolutionary change. This change will likely be a speciation event. This is a lineation-splitting event that produces two or more separate species from one (think about the branching on the tree of life). Usually we think of speciation as occurring via a geographic isolation (birds on different islands, populations separated by a mountain range, etc.), but the niche variation hypothesis allows for sympatric speciation because the exploitation of different resources splits a population within the same habitat. Admittedly, this type of selection would need to be really strong and stable over a long period of time to cause speciation. Now on to the study!

Killer whales (Orcinus orca) are actually members of the dolphin family (Delphinidae). They are the most widely distributed cetacean species in the world and are top marine predators. Males typically live about 30 years on average, and females about 50 years. The diet of killer whales is often geographic or population specific. Populations of orcas are usually defined as either “residents” or “transients.” As the name suggests, residents tend to stay in a more localized area whereas transients travel over large distances, sometimes overlapping with the ranges of resident populations. It has been documented that these different types of populations vary greatly in their diets, each consuming a narrow range of prey. Residents feed primarily on fish while transients feed nearly exclusively on other marine mammals. Considering this, and what we know of how the niche variation hypothesis cause speciation, have or are killer whales branching in to two species?

One of the problems in answering this question is the long-lived nature of these animals. It’s difficult to see a long-range change on a long-lived species. Most evolutionary studies use either comparisons at a single point in time or over timescales representing one to a few generations. Okay, that’s pretty good, and these snapshots have been very informative, but to get a real-time view in a long-lived species you really need to go small. And by that I mean molecular. Ancient DNA (aDNA) and stable isotope data from subfossil (remains that have not completed the fossilization process) specimens can be used to track niche and evolutionary history. The scientists in this study used these methods to look at the evolution in sympatric killer whale populations in the North Sea. First, they sampled 23 subfossil killer whale bones and teeth recovered by dredging or trawling the Southern Bight of the North Sea or from archaeological sites in Southern Scandinavia. Then they dated their samples using radiocarbon techniques or archaeological context. Next, they used stable isotope ratios to provide a long-term measure of what the animals ate during their lifetimes and thereby estimate the orcas’ niche width (it is argued that populations in wider niches are more variable than populations in narrower niches). Additional evidence of these dietary habits was gathered from examining the wear-patterns on the teeth (for example, feeding heavily on herring badly wears down the teeth). Then mitochondrial DNA (mtDNA) sequencing was used to determine the degree of linage sorting (separate populations carry their genetic diversity with them) based on isotopic (prey) niche. And finally, they biopsied the skin of modern orcas, sampling either while the animals fed on fish or on stranded remains with known stomach contents. From this they were able to extract high-quality DNA and conduct an individual-based analysis of population structure. This, combined with the aDNA data, effectively gave them a map of the evolutionary outcome of niche variation.

This is one of those studies where the results are all variable. *sigh* ‘Tis science. From the isotopic analysis, the researchers found  a lot of overlap in the results, mostly likely explained by among-individual differences. Because this type of analysis represents what an animal ate over its lifetime, differences in prey items within the diets of individuals are not apparent. This and the analysis of tooth wear suggests some overlap either in the diet and/or foraging method of the specimens studied. The result is consistent with the observations of the modern whales. Fish eating pods are often found with mammal remains in their stomach contents. Lineage sorting of mtDNA sequences based on the isotopic values revealed that there “has been multiple diversifications [sic] in isotopic niche” and “an indication there was relatively stable transmission of isotopic niche along matrilineal lines within some clades, in particular those that were dominated by samples from Norway.” The incomplete lineage sorting they found seems to be consistent with relatively recent divergences in niches, and their models indicate panmixia (random mating) between at least some groups that feed on fish and some groups whose diet includes seals.

To sum up, we know that there is niche variation in populations of killer whales. But all of that variation and overlap that the researchers found suggests that any speciation is still at an early stage in this system. And while the results of this study seem to be all over the place, it does add more information to the story while providing a useful long-term evolution study methodology. It also strengths the argument that sympatric speciation is difficult to achieve.

Also check out this great presentation on this study!



Foote, Andrew D., Newton, Jason Newton, Ávila-Arcos, María C., Kampmann, Marie-Louise, Samaniego, Jose A., Post, Klaas, Rosing-Asvid, Aqqalu, Sinding, Mikkel-Holger S., & Gilbert, M. Thomas P. (2013). Tracking niche variation over millennial timescales in sympatric killer whale lineages Proceedings of the Royal Society B, Biological Sciences, 280 (1768) DOI: 10.1098/rspb.2013.1481

Science's article "North Atlantic Killer Whales May Be Branching Into Two Species"

For more information and explanation of some of the evolutionary terms discussed this post see:
Understanding Evolution via Berkeley, particularly the page on sympatric speciation
and for a nice description and examples of niche variation see
Soule, M. and Stewart, B.A. (1970) The "Niche-Variation" Hypothesis: A Test and Alternatives. The American Naturalist, 104(935): 85-97. (LINK)

Some useful resources for information on killer whales:
NOAA Fisheries Office of Protected Resources page on Killer Whales
National Marine Mammal Laboratory's page on Killer Whales
Cascadia Research Collective's "Studying the diet of fish-eating killer whales"


(image via National Geographic, photo credit Gerard Lacz/Animals Animals—Earth Scenes)

Om Nom Nom: The Links Between Plant Diversity and Herbivory

I usually start a post with the reason why a particular article caught my eye. Today, I’m not sure why my eyeballs glommed on to this paper, but they did. As it turns out, they have a pretty good taste in articles. Who knew?

An early view paper from the Journal of Ecology looks at how the large herbivores of the African savanna affect the diversity and community structure of plants. More and more studies these days are taking a phylogenetic approach to community ecology questions. That is, they are looking at the evolutionary development and history of a species or taxonomic group to explain the patterns that we currently see. This new study takes this approach in the subtropical woodland biome, or “bushveld,” of the Kruger National Park (KNP) in northeast South Africa. This area is home to 148 mammal species, of which 30 are large herbivores such as elephants, rhinos, and giraffes. The vegetation of this area consists of 1974 species, including 458 species of trees and shrubs. KNP varies from dense thicket, savanna woodlands to forests characterized by tall trees and a closed canopy. These plant communities are under occasional pressure from periodic fire and under constant pressure from large herbivores. This study looks at the impacts of these herbivores on the phylogenetic structure of woody plant assemblages and evaluates the impacts of their removal on plant community composition and structure.

The researchers used DNA sequencing to reconstruct the phylogeny of 448 species of trees and shrubs (using Amborella as an outgroup), representing 246 genera, 71 families and 31 orders. ... Let’s pause for a second to say “Wow!” ... Then they calculated divergence times and used speciation models on these data. Next was the community sampling along a north-south transect through KNP. This transect has enclosures situated along it where large herbivores are partly or fully excluded. These enclosures have been established in the park for between 8 and 43 years. Within 15 defined “ecozones,” the researchers surveyed 110 50x50 meter unrestricted herbivory plots and 15 50x50 meter plots in each of the five herbivore exclusion enclosures. Within these plots they recorded all species of trees and shrubs and the number of individuals per species (abundance). Then they evaluated various physical and mechanical plant defense traits (not including chemical defenses), using wood density of quantify plant resistance to physical damage and specific leaf area (SLA) as a proxy for leaf nutrient content.

All sorts of indices (MPD, MNTD, SR, Shannon, NRI, NTI) and statistics were used that I’m not going to go into because they will just confuse everyone. But when all the statistics were done, they found a latitudinal gradient in diversity with the highest diversity in the south and extreme north and low diversity in the center (which matches rainfall patterns). In parallel, they found shifts in community phylogenetic structure comparable to these changes in community diversity, indicating that the communities in the center are more highly phylogenetically clustered (composed of more closely related species). Plant diversity in the KNP is strongly spatially structured and this clustering is reflective of generalist browsing, the geomorphology of the area, and the patchy distribution of large herbivores. In plots where herbivory is unrestricted they found significant phylogenetic clustering of plant communities, likely the result of the heavy pressure from the herbivores. They also found that plant defense traits had a weak but significant phylogenetic signal, suggesting that they do not fit well into the simple model they used. When the researchers compared the enclosures to the unrestricted areas they found “that when megaherbivores are excluded, species diversity generally decreases, but changes in phylogenetic diversity [vary] by spatial location.” When large herbivores are excluded, plant community structure is contingent upon the initial community structure. If a community was initially overdispersed then the shift towards a more clustered community would occur by excluding large herbivores and vice versa. Ultimately, they conclude that the exclusion of large herbivores results in impoverished species communities.

I think that it is important to mention that these researchers were limited by the study design they had to work with. These enclosures had already been set up by other people. As such, the scientists encountered some issues that they would have been able to control for if they had set up the site themselves. Issues like enclosure age and location. For example, one enclosure was located on a river that periodically floods, altering local plant diversity. Such issues make it difficult for them to predict how specialist vs. generalist herbivores impact community structure and prevents them from drawing strong conclusions about the underlying causes for the patterns they saw.

On the upside, their results add valuable knowledge critical for predicting the impacts of overall herbivore decline on African ecosystems and local increases of these animals in protected reserves. This study “shows not only that large herbivores are key to maintaining woody plant diversity, but also that they may impose specific phylogenetic structure on plant communities.” Shifts in this structure have downstream consequences in that phylogenetic diversity can capture genetic and functional diversity, which has been linked to ecosystem productivity. And, ultimately, we want to keep our ecosystems happy and productive, right?


Kowiyou Yessoufou, T. Jonathan Davies, Olivier Maurin, Maria Kuzmina, Hanno Schaefer, Michelle van der Bank, & Vincent Savolainen (2013). Large herbivores favour species diversity but have mixed impacts on phylogenetic community structure in an African savanna ecosystem Journal of Ecology : 10.1111/1365-2745.12059


(image via Animals Time)

The Silverback Playbook: Changing Climate and Ape Distribution

On occasion, I go back to my roots in biogeography and peruse that subset of journals for interesting articles. Admittedly, I now skip over some topics that I used to devour, such as the species-area relationship (the "most general, yet protean pattern" that has recently warranted a special virtual issue). These days, I tend to stop and read articles about distribution patterns, especially as they relate to current problems like climate change.

There are an increasing number of studies that show that climate change will affect species distribution patterns and biodiversity patterns in general. Temperatures, rainfall patterns, sea level changes, etc. are likely to cause geographic shifts in the ranges of plants and animals, altering their relationships with the environment and other species. The common methods for predicting these effects are called bioclimatic envelope models. Basically, these models try to determine the "climate envelope," a description of the climate that defines a species' range, and then map the geographic shift of that envelope under climate change. These types of models are useful for predicting distribution patterns, but they do not inform us about the underlying mechanisms that limit species' distribution and how species will change their behavior and/or the kinds of habitats where they can survive. Think about this behavior part a little more in depth, specifically taking brain size into account. It has been shown that large-brained species are better able to cope with seasonal changes in their environments, buffering themselves against modest levels of climate change, and are more resistant to extinction.

When you think of large-brained species, which ones come to mind? Probably the primates, specifically the African apes (gorillas and chimpanzees). What do we already know about these species? We know that they live in Africa (the most vulnerable of all continents to the effects of climate change), occur in similar habitats (although they differ somewhat in biogeographical ranges), are highly endangered, have highly restricted ranges, have a slow life history, have a large body mass, and have somewhat similar diets. Knowing this, how do you think climate change will affect them?

A study published in the Journal of Biogeography takes a look at how the behavior and distribution of African apes will be affected by climate change. They use a time budget model to investigate how climate warming and behavioral flexibility might affect ape survival. Time budget models are based on individual behavior, how much of an individual animal's time is spent on feeding, resting, traveling and socializing. An animal's time is limited (there is only so much time in a day) and so there is a constraint on the size of a group that can be maintained in a particular habitat which ultimately determines a species' distribution. These types of models can predict distribution as well as the bioclimatic envelope models, as they are based on simple climatological variables, with the added advantage of providing informing us about mechanisms of keeping a species in a particular habitat and evaluating the level of ecological stress in areas where it does occur. They applied this model to data from 20 natural populations of gorillas (Gorilla beringei and Gorilla gorilla) and chimpanzees (Pan troglodytes and Pan paniscus). The model looked at the relationship between climate, group size, body weight, and time budgets. They ran the model to predict ape distribution across Africa under a uniform worst-case climate change scenario, highlighting the importance of individual behavioral requirements for survival. I'm going to save you lengthy descriptions of the model parameters, time budget equations, and model testing. You can thank me later.

The study found that gorillas are more restricted by temperature variation than are chimpanzees. This may cause gorillas to suffer more strongly from the effects of global warming. Their larger body mass and smaller group sizes also increase their risk of extinction even with their behavioral flexibility. This doesn't mean that the chimps are unaffected. They found that chimpanzee communities will be significantly reduced even at locations where they are predicted to survive. The model showed that two critical factors may ultimately determine their survival at these locations: minimum viable community size and minimum party size. Although the distribution for both genera is in the downward direction, the two taxa are predicted to respond differently to changes in climate. Chimpanzees are expected to primarily suffer a reduction in community size because they will need to spend an increasing amount of their time moving and resting. And considering that minimum viable community size is one of the two critical factors, chimps will find it difficult to survive in any of their present habitats and may even go extinct. On the other hand, gorillas already live in small groups and when combined with a dramatic reduction in available habitat (again with the moving and resting time), climate change is predicted to have a stronger effect on their biogeography. However, the authors think that the few surviving populations should be able to maintain present-day group sizes, making them locally stable. Even if the changes in climate were not as extreme, the researchers think that their model would still predict that apes will suffer habitat loss simply due to time budgeting problems that may be reinforced by indirect effects (like temperature on leaf quality). Sure, behavioral flexibility may help, particularly with the more socially fluid chimpanzees, but the environment will support only what it can support (especially for hungry, large bodied creatures).

It is important to note that this study does not include anthropogenic (human caused) influences. Couple those with the doom-and-gloom predictions that the study already makes and it looks like it's bye-bye time for the big apes. That is a bit of a depressing note to leave the post on. Perhaps the good (or happy?) note to leave on is that studies such as these (that take mechanism into account) can give us better ways to predict and preserve optimal habitats, ultimately finding ways to best conserve these species. After all, that is the goal right?


Lehmann, J., Korstjens, A., & Dunbar, R. (2010). Apes in a changing world - the effects of global warming on the behaviour and distribution of African apes Journal of Biogeography, 37 (12), 2217-2231 DOI: 10.1111/j.1365-2699.2010.02373.x


(image via earthtimes.org)

Scrat in Real Life

Have you seen the Ice Age movies? If you are like me then Scrat, the neurotic saber-toothed squirrel, is your favorite character. That poor squirrel just can't hold on to his acorn. According to a new paper published in Nature, Scrat may be closer to a real prehistoric creature than the animators realized, anatomically speaking at least.

Meet Cronopio dentiacutus. A fossil from the La Buitrera locality, Río Negro Province, Argentina was identified as a medium-sized dryolestoid, with an extremely enlongated snout and a pair of curved saber-fangs.  Dryolestoids are an extinct mammalian group belonging to the lineage that leads to modern marsupials and placentals. They thrived in South America through the Mesozoic and into the Cenozoic. This specimen was of the early Late Cretaceous (60 million years from previously known), and based on it's dental and cranial features, is unlike previously identified specimens from the Mesozoic.

Artist depiction of Cronopio dentiacutus

Unfortunately for this Scrat-like critter, there were no acorns in the Cretaceous.

The paper:
Rougier, Guillermo W., Sabastiam Apesteguia, and Leandro C. Gaetano (2011) Highly specialized mammalian skulls from the Late Cretaceous of South America. Nature: 479, 98-102. (DOI: 10.1038/nature10591)

ScienceShot Article: Meet the Saber-Toothed Squirrel

Resetting the Molecular Clock

Figure 1a

 Ya know, I haven't done a new creature feature in a while, and while I was flipping (and by that I mean scrolling) through the table of contents of the newest issue of Nature I came across a rather interesting new eutherian.

The therian mammals include placental mammals and marsupials. All of these animals can be distinguished by the number, morphology, and replacement pattern of their teeth. Eutherians are the true placental mammals. That means they bear live young that developed in and been nourished by a placenta within the mother's uterus, and unlike marsupials (or metatherians, which have a short-lived placenta) the eutherians' placenta contributes significantly to fetal nourishment. This group became common in central Asia during the Upper Cretaceous, and with exception of Australia (where marsupials rule), they have been the largest and most common land vertebrates following the end of the Mesozoic.

This new paper in describes a new species of eutherian the authors are naming Juramaia sinensis, a shrew-like animal alive during the Jurassic period. The fossil was discovered in the Liaoning Province in northeast China and is comprised of an incomplete skull including teeth, part of the skeleton including forepaw bones, and impressions of residual soft tissues such as hair. Juramaia is among the earliest known eutherians, and is a group that evolved to include all other placental mammals. It has adaptive features such as scansorial forelimbs that are good for climbing. When a majority of your mammalian cousins scuttle around on the ground, the ability to climb works to your advantage in evading predators and finding food. The fossil also provides the ancestral condition for dental and other anatomical features of eutherians.

This fossil find is so important because it "establishes a much older geological time for the split of the metatherian-marsupial and the eutherian-placental lineages than previously shown by the fossil record." J. sinensis is dated at 160 million years. Previously the earliest eutherian record is Eomaia and the metatherian record is Sinodelphys, both of which are 125 million years old. Parsimony analysis show Juramaia to be more closely related to extant placental mammals than to all other metatherians. This placement of Juramaia on the placental side of the marsupial-placental divergence means that the divergence itself must have occurred before Juramaia evolved. Add together the older age of the fossil and the parsimony analysis and you get a marsupial-placental divergence date that was at least 35 million years older than anyone previously thought. As it turns out, getting the timing of this divergence right is critical for calibrating the rates of evolution for all therian mammals. It is particularly useful for scientists doing molecular evolutionary studies and comparative genomics and their work in determining a "molecular clock." So far, there has been a discrepancy between the previous fossil record and the molecular age for the marsupial-placental divergence. Molecular studies have provided estimates of fossil ages between 143-178 million years which did not match up with the fossil evidence at the time. This new fossil now corroborates the molecular findings and sets the minimal divergence time to coincide with the molecular time estimates.

Love when things match up.

Here's the paper:
Luo, Zhe-Xi, et al. (2011) A Jurassic eutherian mammal and divergence of marsupials and placentals. Nature: 476, 442-445. (DOI: 10.1038/nature10291)

and...
http://www.sciencedaily.com/releases/2011/08/110824131535.htm

Batting a Billion

Did you know that 2011-2012 is the Year of the Bat? Thanks to classic literature and popular culture, bats are thought to be nocturnal, creepy, winged rats. Probably every fear people have concerning bats is based on centuries of myths and misinformation. As part of my what-is-becoming-typical subject introduction I thought I'd give some facts and dispell a few of the myths about bats with a little round of True or False. As I plan to present a paper here and not just a bunch of bat facts I'll try to keep to some of the most popular myths and at the end of this post I'll have some links where you can find out more information.

True or False?: Bats are mammals.

TRUE

Bats are flying mammals belonging to the order Chiroptera. There are more than 1,100 species (that's 1/5 of all mammals!), including the world's smallest mammal, a bat the size of a bumblebee.

True or False?: Bats are blind.

FALSE

Actually many bats have very good eyesight. However, because many species are nocturnal (active at night) they have an extra sense that helps them to navigate and find food: echolocation. They send out sound which bounces back off of objects and creates a sort of map for the bat.

True or False?: All bats feed on blood.

FALSE

Well, mostly. Admittedly there are three species of vampire bat: the Common Vampire Bat (Desmodus rotundus), the Hairy-legged Vampire Bat (Diphylla ecaudata), and the White-winged Vampire Bat (Diaemus youngi); all of which are found in Latin America. But don't worry, they don't require much blood and typically like to feed on livestock. More than two-thirds of bat species are primary predators of night-flying insects, this includes agricultural pests and many insects humans find to be particularly disruptive or annoying. A single bat can eat up to 1,000 mosquito-sized insects in a single hour! The other third of bat species feed on the fruit and nectar of plants. As such, they serve as pollinators and seed dispersers for many plant species. A small percentage are also known to eat fish, frogs, mice, birds and/or other small vertebrates.

True or False?: Bats are found everywhere.

FALSE

Close but no. Bats are a very diverse group that take advantage of a wide variety of habitats, but they do not inhabit extreme desert and polar regions.

True or False?: Bats live in caves.

TRUE

You can find many bat species living in caves. This is because one of the most basic requirements for bat is a safe roost. As such, bats can be found living in almost any conceivable shelter, from caves to buildings to leaf cavities and even in animal burrows. As their habitats shrink, more and more species, and individuals, can be found living in buildings. Building bat houses, the same concept as a bird house, is a backyard conservation technique that is catching on with the public. (Learn how to build you own bat house here: http://www.batcon.org/index.php/get-involved/install-a-bat-house.html)

The questions that I've listed here are not only some of the most popular concerning bats, they are also directly related to today's topic. A new Policy Forum paper published in Science this week takes a look at bat conservation from the aspect of their economic importance.

It is known that White-nose Syndrome (WNS) and the increased development of wind-power facilities are threatening populations of bats in North America. WNS is a fungus (Geomyces destructans) that infects the skin of cave-dwelling bats while they hibernate, particularly around the nose, ears, and wings. It is associated with a high mortality rate and is estimated to have killed over a million hibernating bats in more than 15 U.S. states and 2 Canadian provinces. Little Brown Bats (Myotis lucifugus) are sustaining the highest mortality rates, showing a 93% decline in 23 caves at the epicenter of the WNS outbreak. Other species affected include the Big Brown Bat (Eptesicus fuscus), Northern Myotis (Myotis septentrionalis), Tri-Colored Bat (or the Eastern Pippistrelle, Pipistrellus subflavus), Eastern Small-Footed Myotis (Myotis leibii), and Indiana Bat (Myotis sodalis).

Our growing concerns about climate change mixed with our desire to break our dependance on oil have resulted in the construction of more wind turbines. As a source of alternative energy wind turbines are a wonderful thing. However, for species of migratory tree-dwelling bats they are a flight, and life, hazard. In North America, these species include the Eastern Red Bat (Lasiurus borealis), the Hoary Bat (Lasiurus cinereus), and the Silver-haired Bat (Lasionycteris noctivagans). Other species that are ssusceptible to wind turbines include the Tri-colored Bat (L. subflavus), the Little Brown Myotis (M. lucifugus), and the Big Brown Bat (E. fuscus), species names that should sound familiar after reading about WNS. Included in this list of affected species includes bats with a relatively small range sizes, the Mexican Free-tailed Bat (Tadarida brasiliensis) and the federally endangered Indiana Myotis (M. sodalis). High numbers fatalities in species with small range sizes has a greater impact on the survivability of the species than the same number of fatalities in populous, large-range species. It is still unclear why these species are so susceptible to wind turbines. There is no continental-scale monitoring programs for assessing wildlife fatalities caused by wind turbines, but it is predicted that by 2020 an estimated 33,000 to 111,000 bats will be killed by wind turbines just in the Mid-Atlantic Highlands of the U.S.

This article focuses on these two sources for declining bat populations, leaving out sources such as habitat degradation. The numbers of bat fatalities are, in and of themselves, pretty staggering, but many people in political and policy making positions still consider it an academic interest rather than an economic problem. That is where this article becomes particularly interesting. In fact, the economic consequences of losing so many bats could be substantial. One example the authors use is the Big Brown Bat (E. fuscus). A single colony of 150 bats in Indiana as been estimated to eat nearly 1.3 million pest insects per year. Think about it: That is one relatively small colony of bats eating a whole lot of insects. Other estimates have a single Little Brown Myotis (M. lucifugus) consuming 4 to 8 grams of insects each night. Doesn't sound like much, but if you extrapolate that from one bat to one million bats that is 660 to 1320 metric tons of insects. This is a huge disruption to the population cycles of agricultural pests, and to say that bats are unimportant is just ignorant. 

The paper goes on to discuss the economic importance of bats in agricultural systems, estimating the value of the pest suppression services provided by bats. Previously published estimates have the value at anywhere from $12 to $173 per acre, with a likely value at $74/acre in a cotton-dominated landscape in south-central Texas. The authors here took these values and extrapolated the estimates to the entire United States. They estimated that the value of bats to the agricultural industry at between $3.7 billion and $53 billion per year with a likely value of approximately $22.9 billion per year. This cost does not include any downstream impacts of bat loss such as the impact of pesticides, secondary predation, and the predator release of insect populations.

A figure describing the worth of bats. Yellow being low cost to red being high cost.

 In terms of policy, the authors suggest that wait-and-see approach to the issue of widespread declines of bat population is unacceptable as the life histories of these mammals suggest that population recovery is unlikely for decades or centuries, if at all. They suggest management actions to restrict the anthropogenic spread of WNS, taking additional steps toward developing improved diagnostics to detect early stage infections and fungal distribution, investigating biological or chemical control of the fungus, increasing disease resistance through habitat modification, potentially culling infected bats, altering wind turbine operations during high-risk periods for bats, and continued research into these problems.


Here's the article:
Justin G. Boyles, Cryan Paul M., McCracken Gary F., and Kunz, Thomas H. (2011) Economic Importance of Bats in Agriculture. Science: 332 (6025), 41. (DOI: 10.1126/science.1201366)

GENERAL INFORMATION ABOUT BATS:
Description of bat species from the Smithsonian National Museum of Natural History:
http://www.mnh.si.edu/mna/image_menu.cfm?order=4
Info on bats from the Natural Science Research Laboratory at the Museum of Texas Tech University: http://www.nsrl.ttu.edu/tmot1/ordchiro.htm
The Year of the Bat website:
http://www.yearofthebat.org/
From Boston University's Bat Lab: http://www.bu.edu/cecb/bats/bat-facts-and-folklore/
From the Museum of Palentology at UC Berkeley:
http://www.ucmp.berkeley.edu/mammal/eutheria/chiroptera.html
A list of academic "bat labs": http://www.science.mcmaster.ca/psychology/faurelab/links

BATS AND WIND ENERGY:
From Bat Conservation International:
http://www.batcon.org/index.php/what-we-do/bats-and-wind-energy.html?utm_source=internal&utm_medium=five_icon&utm_campaign=5IBats%2B%26%2BWind%2BEnergy
Bats and Wind Energy Cooperative (BWEC): http://www.batsandwind.org/
Video and information from Boston University about bats interacting with wind turbines:
http://www.bu.edu/cecb/wind/video/
U.S. Department of Interior, US Fish and Wildlife Wind Turbine Guidelines Advisory Committee:
http://www.fws.gov/habitatconservation/windpower/

WHITE-NOSE SYNDROME (WNS):
Buzbee's Bathouse Page:  http://www.batbox.org/
Info from the U.S. Fish and Wildlife Service: http://www.fws.gov/WhiteNoseSyndrome/
From the Organization for Bat Conservation:
http://www.batconservation.org/drupal/white-nose?gclid=CKy6l6rO-6cCFUNl7Aod6R0srw
USGS National Wildlife Health Center WNS Page:
http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/
The National Speleological Society's WNS Page:
http://www.caves.org/WNS/

BAT CONSERVATION ORGANIZATIONS:
Bat Conservation International: http://www.batcon.org/
Organization for Bat Conservation: http://www.batconservation.org/
Bat Conservation and Management, Inc.: http://www.batmanagement.com/main.html
Lubee Bat Conservancy: http://www.batconservancy.org/
Bat World Sanctuary: https://batworld.org/
Bat Conservation Trust (in the UK): http://www.bats.org.uk/
The Warwickshire Bat Group (UK):  http://www.warksbats.co.uk/
The Norfolk Bat Group (UK): http://www.norfolk-bat-group.org.uk/index.html

(image from discoverlife.org)

Sasquatch Watch

In the science of Sasquatch it's all about distribution. Where is he (or she) and how can I get a photo? The photo I'll leave up to you, and hope you are good at keeping your camera steady to avoid those embarrassingly blurry pictures. The where is he part can be figured out by utilizing user-friendly software, publicly available biodiversity databases, and ecological niche modeling (ENM).

A scientist named Grinnell proposed the ecological niche concept in 1917, so it isn't new. Overall, it's pretty simple. Each species needs a specific set of conditions to survive. The range where these conditions occur is where a species can maintain a population. Since 1917 the concept has been expanded, most notably by Elton in 1927 and MacArthur in 1972, to include a species as part of an ecological community. With this type of model it is possible to characterize the ecological needs of a species, predict and anticipate it's distribution, predict changes in it's distribution with changing land and climate, investigate patterns of speciation and niche divergence, and build scenarios for unknown conditions and behavior. "The basic premise of the ENM approach is to predict the occurrence of species on a landscape from georeferenced site locality data and sets of spatially explicit environmental data layers that are assumed to correlate with the species’ range." That's how the paper I'm presenting today describes it. What does it mean? Input known, locally collected data and make reasonable predictions of species occurrences given the current modelling technology. That known, locally collected data is becoming more and more available and accessible via museum databases and online data portals.

Sasquatch, or Bigfoot, is currently (pseudo-)classified as a member of a large primate lineage descended from the extinct Asian species (Gigantopithicus blacki), but there is some phylogenetic analysis indicating a possible membership in the ungulate clade. Regular reports have Sasquatch inhabiting the forested lands of western North America, although a type specimen is unavailable. This paper, from the Journal of Biogeography, presents ENMs for Sasquatch. They base their ENMs on putative sightings, auditory detections, and footprint measurements primarily obtained from the Bigfoot Field Researchers Organization (BFRO). Events were assigned geographic coordinates on USGS quad maps and atlases and the ENMs constructed using the maximum entropy niche modelling approach using the software MAXENT. Then environmental layers were constructed for 19 BIOCLIM variables in the WORLDCLIM dataset. The final set of environmental variables included annual mean temperature, mean diurnal range, isothermality, temperature annual range, mean temperature of wettest quarter, mean temperature of driest quarter, precipitation seasonality, precipitation of driest quarter, and precipitation of coldest quarter.

The ENM showed that Sasquatch should be broadly distributed in western North America, with a range comprising such mountain ranges as the Sierra Navadas, the Blue Mountains, the Selkirk Mountains, and the Cascades. The bioclimatic variable that was the best predictor was precipitation in the coldest quarter. And so, it is likely that the distribution will be altered due to global climate change.

Running with that result, the scientists examined the potential ramifications of climate change on remnant Sasquatch populations to predict how the frequency of sightings might change in the future. To do this they projected ENMs generated from the WORLDCLIM data into bioclimatic layers simulated for a doubling of atmospheric CO2. The model predicts that Sasquatch will abandon lower altitudes and lose habitat in coastal regions. But the species will potentially gain habitat in the northern part of the range as well as in several other montane areas. This means that, in the future, you should expect to sight Bigfoot in northern latitudes and at higher elevations.

Another suggestion: Look for American black bears (Ursus americanus) and you may sight Sasquatch. Now, I'm not advocating lurking around bear dens or walking right up on a black bear, but the predicted distribution of Sasquatch is similar to the range of the American black bear. So much so, that it is thought that some Bigfoot sightings were, in fact, misidentified black bears.

Up for a hike in California? Bring your camera.
Here's the paper:
J. D. Lozier, Aniello, P., and Hickerson, M.J. (2009) Predicting the distribution of Sasquatch in western North America: anything goes with ecological niche modelling. Journal of Biogeography: 36(9), 1623-1627. (DOI: 10.1111/j.1365-2699.2009.02152.x)

This story to your liking? Then take a look at my story from back in April 2010 on modeling the outbreak of a zombie infection :-)
http://storiented.blogspot.com/2010/04/mmmmbrains.html

Tiger Tales

Tigers are the largest of the Asian big cats. There are currently 8 recognized subspecies of tiger (Panthera tigris):

1. Amur (Siberian) tigers (Panthera tigris altaica)
2. Bengal (Indian) tigers (Panthera tigris tigrisn)
3. Indochinese tigers (Panthera tigris corbetti)
4. South China tigers (Panthera tigris amoyensis)
5. Sumatran tigers (Panthera tigris sumatrae)
6. Bali tigers (Panthera tigris balica)
7. Javan tigers (Panthera tigris sondaica)
8. Caspian tigers (Panthera tigris virgata)

In the past tigers ranged across Asia, northern Iran, Afghanistan, Thailand, Vietnam, Laos, Cambodia, Malaysia, parts of Pakistan, and the islands of Bali and Java. These days tigers are not so common and wide ranging. In fact, they are extinct in most of these areas with the Caspian, Bali, and Javan tigers completely gone. Some populations are more stable than others, but the remaining subspecies are in danger due to the illegal wildlife trade, poaching, and conflict with people.

Here, I'm going to focus on the Bengal Tiger (Panthera tigris tigris) which are found mostly in India. Since 2008 the Bengal Tiger has been listed by the IUCN (International Union for Conservation of Nature) as Endangered. India has recently revamped its national tiger census methodology to include more updated and scientific methods. They are now using camera trap and sign surveys using GIS to extrapolate site-specific tiger densities. The results of this work (which includes some areas outside of India) has estimated the current tiger population of India at 1,411 adult/sub-adult tigers. Now, when it comes to conserving the genetic diversity of tigers, biologists like to quantify the breeding population (the number of animals raising offspring to reproductive adulthood). The breeding population of Bengal Tigers has been estimated at just 40% of the adult population. Why such a small number? Likely it is due to the small ranges which are not large enough to support an effective population, and those ranges are still shrinking.

There are all sorts of tiger conservation groups out there. They are all very interesting and most very worthy of donating to, but today I'm going to talk about some interesting programs at colleges and universities. There are a few American universities that have the tiger as their school mascot: The University of Missouri, Clemson University, and Auburn University. To save the animal that is also their mascot they have each created organizations to help educate themselves and others about this endangered animal. Recently, these schools have also joined forces with WWF (World Wildlife Fund) and its work in protecting the tiger. WWF has given these schools the challenge of raising $75,000 to help end the illegal tiger trade in China and the Eastern Himalayas. As of today $7,446 has been raised, with Auburn University in the lead.

Let's take a quick look at the goals of these individual groups, and I'll give you the links to their websites so you can learn more about them and possibly help them out.

University of Missouri:

In 1998 an Michael Baltz, a PhD student in biological sciences, wrote an editorial for the Columbia Daily Tribune where he suggested that students could take the lead in implementing a program that would support the conservation of their mascot. Soon after, in 1999, Mizzou Tigers for Tigers was organized. It was the nation's first tiger mascot conservation program. Here, faculty, staff, students, and alumni work together to conserve wild tigers. This organization works to raise awareness about the endangered status of tigers by working with local schools and educating students about conservation on a global scale. They bring in experts in the field to present public lectures on tigers and tiger conservation, and they also work to raise funds to aid in conservation efforts.

Goals: Raise awareness about the conservation status of wild tigers, fund projects benefiting wild tigers and people living near tigers, and enhancing educational and research opportunities for the university's students while contributing to tiger conservation.

University of Missouri Tigers for Tigers Homepage: http://tigers.missouri.edu/
This organization works closely with the Save the Tiger Fund: http://www.savethetigerfund.org/

Clemson University:

A Clemson student returning from a trip to India decided to start a student organization to help wild tiger conservation efforts. This was the beginning for Clemson Tigers for Tigers. The organization struggled its first few years but grew to become a special topics class within the Biological Sciences department, bringing in experts to speak, volunteering at the Central Florida Animal Reserve, and even takes students to India to tour and learn about various tiger conservation initiatives. The club includes a "Cubs for Cubs" program that teaches local school-aged children about wild tigers, the "Adopt-a-Park" program which is leading towards sponsoring a tiger reserve in India, and, of course, fundraising.

Goals: Increase awareness and interest in tiger-range countries and enhance Clemson's reputation for social responsibility and public service.

Clemson Tigers for Tigers Homepage: http://people.clemson.edu/~t4t/
An article in Clemson's school paper The Tiger: http://www.thetigernews.com/news.php?aid=2654&sid=4
This organization works closely with the Tiger Trust: http://www.tigertrustindia.org/

Auburn University:

Auburn also has a Tigers for Tigers organization. It is part of their chapter of The Society of Conservation Biology. Members of the organization work with local outreach programs and the Montgomery Zoo to provide activities for their various educational programs. They are trained by and work with Project WILD, one of the most widely-used conservation and environmental education programs among educators of students kindergarten through high school. They use the tiger to teach students about conservation on a global scale and use these themes to education students on conservation closer to home.

Goals: Raising funds for the conservation of wild tigers, becoming a partner in a nationwide Tigers for Tigers program, and educating on conservation in Auburn schools.

Auburn Tigers for Tigers Homepage: http://www.auburn.edu/student_info/societyconbio/tigersfortigers/index.html

You would like to help? Easy. You can visit WWF's page highlighting the Tigers for Tigers challenge and find links to donate to each school's fund here:
http://www.worldwildlife.org/sites/tigersfortigers/index.html

I also recommend visiting the Tiger Trust and the Save the Tiger Fund websites I linked to above. Additionally, you can donate $10 to WWF's tiger conservation fund by texting TIGERS to 20222.

(image from bioweb.uwlax.edu)

On Thin Ice

When it comes to charismatic megafauna, polar bears are right up there in terms of cute stuff people like to like. Lately they have also been the poster-bear against climate change. That makes sense, considering that polar bears (Ursus maritimus) occur only in the Northern Hemisphere and are dependent on sea ice for access to their marine mammal prey, mainly seals. Declines in summer sea ice have been associated with declining physical stature, declining physical condition, poorer survival rates, and declining population sizes for these bears. This sea ice decline has been linked to these declines.

A new paper this week in Nature uses projections of twenty-first century global mean surface air temperature (GMAT) and data from the Community Climate System Model (CCSM3) to test the hypothesis that a tipping point will lead to irreversible loss of seasonal ice habitat as GMAT increases. Basically, that there are some elements/variables within a system that, when changed enough, cause habitats that support cold-dependent species to disappear abruptly and irreversibly. Namely when a particular GMAT is exceeded.
 
In a nutshell, they tested whether mitigating the rise in greenhouse gases could improve the outlook for polar bears.
 
Now, a USGS study in 2007 concluded that two-thirds of the world's polar bears could disappear by 2050 if atmospheric temperatures continue to increase due to greenhouse gases. Their model was a general circulation model (GCM) that projected losses of Arctic sea ice based on the Special Report on Emissions Scenarios (SRES) and a "business as usual" greenhouse gas emissions scenario, where emissions continue to increase and the carbon dioxide concentration reaches 689 parts per million (ppm) by the end of the century. However, they did not consider the possible benefits of greenhouse gas mitigation. Think about that in terms of tipping points. If you mitigate too little and/or too late then you get no conservation benefits for polar bears as their ice would already be gone. If you mitigate more and/or soon enough then you save the ice and the bears. That's the thought anyway. So the researchers modeled 5 different scenarios that ranged from "business as usual" all the way to aggressive cuts that reduce carbon dioxide concentrations to 368 ppm, those seen in the year 2000.
 
The study concludes that mitigating the rise in greenhouse gases will result in substantially more sea ice habitat being retained. The business-as-usual-model shows a 50% loss of sea ice by 2050 whereas the aggressive-mitigation-model shows only a 20% loss. They also show that this habitat retention, in turn, will allow polar bears to persist throughout the century in greater numbers and in more areas. The business-as-usual-model shows a 50-80% chance of polar bears disappearing from these habitats whereas the aggressive-mitigation-model shows only a 25-50% chance. However, the models did not give the thresholds or tipping point values that will lead to irreversible ice loss. They found that sea ice will decline at a steady rate as global mean annual temperature rises.
 
The paper also addresses positive feedback in this system. Its all about albedo, or how strongly a surface reflects light. Its really a quite logical scenario. Ice reflects light very well, warmer temperatures cause ice to melt, retreating ice means less reflective surface, retreating ice also means more exposed water, the darker water absorbs more sunlight, more absorbed light increases temperatures, increased temperatures melt more ice. And so on and so on. In this paper they test models that might counter this feedback mechanism. They specifically refer to rapid ice-loss events (RILEs). These rapid freezes result from going from open water to cold conditions reappearing in the Fall, and these compensate for the effects that are working to provide the potential tipping points.
 
Polar bears are not out of the woods yet. After all, we are still running the business-as-usual-model. And, in the past, models predicting sea ice loss have fallen short. But this paper shows us some good news, that with proper mitigation we can potentially slow down the decline.
 
Here's the paper:
Amstrup, Steven C. et al. (2010) Greenhouse gas mitigation can reduce sea-ice loss and increase polar bear persistence. Nature: 468, 955-958. (DOI: 10.1038/nature09653)

Additionally, I suggest reading this paper on polar bear and grizzly hybridization:
Kelly, Brendan P., Andrew Whiteley, and David Tallmon (2010) The Arctic Melting Pot. Nature: 468, 891. (DOI:  10.1038/468891a)
 
Story links:
http://news.sciencemag.org/sciencenow/2010/12/how-to-save-polar-bears.html
http://www.nature.com/news/2010/101215/full/news.2010.675.html
http://www.bbc.co.uk/news/science-environment-11986236
http://www.guardian.co.uk/environment/2010/dec/15/polar-bears-arctic-emissions
http://www.nytimes.com/gwire/2010/12/15/15greenwire-no-tipping-point-for-sea-ice-in-polar-bears-fu-29018.html
 
(image from metro.co.uk)

On the Spot

Have you ever looked at a leopard and wondered why it has spots and not stripes or why it is patterned and not plain? A new study in the Proceedings of the Royal Society B looks at just that question.

The patterns themselves come in a large variety even within the wild cats, and previous studies have suggested that they are for camouflage in these predominantly ambush predators. It is known that hunts are more successful when an attack is initiated from shorter distances. Makes sense. And smaller cats are probably camouflaged for both a hunting advantage and protection from predators. Other studies have also found spots to be significantly associated with arboreality (the presence of trees or a forest or movement within the trees) with dark spots, in particular, associated with closed habitats and predators that prey on ungulates (hooved animals). The conclusions about stripes have been a little less than clear.

The researchers collected images of 35 species of Felidae from the Internet from various wildlife photography resources. They then picked 6 of the best images from each species, images where the animal was shown in profile, full view, free of distortions and occlusions, in focus, in dry weather, and in natural lighting. Then they took rectangular crops of the images using the base of the neck and tail. They then had to classify the images according to the type of pattern they were seeing.

So how do you go about measuring the influence of spots? I mean, consider the jaguar vs. the clouded leopard vs. the serval. All of them have spots, but none of them have the same kinds of spots. So in order to study the evolution of pattern you need to come up with a better way than just calling something spotted. The method used in this study was inspired by reaction–diffusion theories of biological pattern formation. I'm not so much up on those kinds of theories, but here is how the paper describes it:

"Human observers classified standard examples of felid flank patterns to the closest matching comparison pattern in this multidimensional space. The values of variables in the underlying equation that generated the chosen pattern and distribution of observers' classification decisions parameterize the important properties of each standard image. The five dimensions can be conceptualized as: (i) patterned versus plain, (ii) pattern irregularity, (iii) pattern complexity, (iv) pattern element size and (v) the anisotropy (directionality) of pattern elements."

One the measures were characterized they were tested against ecological variables that have been proposed to drive the evolution of pattern phenotypes. These variables include habitat, locomotion, activity time, social systems, prey size, body size, and weight.

After lots of images and lots and lots of stats what did they find? Basically that flank patterns function as camouflage. Okay, not really a new finding, just the same finding with a different method (but the more support for a hypothesis the better right?). They also found that evolution has generally paired plain (unpatterned) cats with relatively uniformly colored, textured, and illuminated environments. Patterned cats were paired with environments that are "full of trees and bushes and stripy, speckly, patchy-blatchy shadows." It is likely that the pattern on the cat resembles the background pattern of the habitat in which it lives or hunts. The cat species living in closed environments and who move around in the trees are more likely to have complex patterns than those who live in open environments and move around on the ground. Felids that have especially irregular patterns live in tropical areas and tend to be nocturnal hunters, preferring to hunt in the trees.

On the topic of stripes, as with previous studies, these authors found no evidence to support the proposition that vertical stripes are associated with grasslands. Considering that the tiger was the only one to be classified as having vertical stripes and its favored habitat is not a grassland, that seems pretty plausible to me.

It wouldn't be a scientific study if you didn't have some outliers to speculate upon. For example, the cheetah (Acinonyx jubatus). This cat has a pattern and yet lives and hunts in a grassland/savanna habitat. Similar outliers include servals (Caracal serval) and black-footed cats (Felis nigripes). On the other side of the coin there are those species who have plain coats but live in closed environments, such as the bay cat (Pardofelis badia) and flat-headed cat (Prionailurus planiceps). Its possible that these outliers could be utilizing different microhabitats within the categories used by this study. Perhaps plain and patterned cats have instances in which the (non-)pattern works and some where it doesn't. Or maybe they are constrained genetically or developmentally. Its difficult to say.

Here's the paper:
Allen, William L., Innes C. Cuthill, Nicholas E. Scott-Samuel and Roland Baddeley (2010) Why the leopard got its spots: relating pattern development to ecology in felids. Proceedings of the Royal Society B: published online. ( DOI: 10.1098/rspb.2010.1734)

If you want to take a look at some of these cats and here patterns then look here:
http://www.zooinstitutes.com/Zoology/family.asp?name=Felidae

And here are some story links:
http://www.bris.ac.uk/news/2010/7264.html
http://www.sciencedaily.com/releases/2010/10/101019212914.htm

(image from webshots.com)

Chase the Squirrel

I was listening to NPR's Wait Wait Don't Tell Me episode in the lab yesterday, and their Bluff the Listener game had a story that made me say "wow, I gotta find that one." The story itself was reported on Live Science and includes a video of Japanese macaques going after a flying squirrel. Basically, the study is about monkeys being annoyed by squirrels. Awesome. They start making threat calls, climb a tree, force the squirrel to glide to the ground, and then chase it once it gets there. The male macaques are thought to be impressing the females in their troop, being tough guys. "It is possible that adult or sub-adult male monkeys may be 'showing off' their fitness" as potential mates, said Kenji Onishi, an assistant professor of behavioral sciences at Osaka University and lead author of the paper being published in the current issue of the journal Primate Research.

Read the rest of the story and watch the video here:
http://www.livescience.com/animals/monkeys-attack-flying-squirrels-100730.html

Bring a Baby

Barbary macaques (Macaca sylvanus) are indigenous to the mid- and high- altitude (1200-2000m) oak, cedar, and scrub forests of Northern Africa mainly in Algeria, Tunisia, Morocco and the Gibraltar peninsula. They are large primates that have silky grey-brown to grey-yellow coats, dark pink faces, and lack a tail. They live in territorial ranges in troops ranging in size from 7 to 40 individuals (usually around 30). They are omnivores that subsist on a diet of tubers, fruits, leaves, rhizomes, seeds, invertebrates, and flowers.

They have a promiscuous mating system in which females mate with all the male members of the group. Females typically remain within their natal groups while males often disperse from these groups. This dispersal behavior in the males is critical for gene flow and the reproductive success of individual males. Every 2 years a female will give birth to a single offspring after a 165 day gestation period, and then the infants will cling to their mothers starting immediately after birth. These young primates are well-developed and will stay and nurse from their mothers for about a year. Male macaques are known to tend to a single young macaque, grooming protecting, and playing with the youngster. After all, with this type of mating system any male could potentially be the father of an infant, so it benefits a male to care for young. Males will establish hierarchies, hierarchies that change with the age of the males and the males that leave or enter the troop.

A new paper in Animal Behaviour describes how male Barbary macaques use infants as “costly social tools.” The researchers noticed that after an infant was born a male would slowly approach the mother and then seize the infant. The infant-toting male would then approach other males in the group, and non-infant-toting males would not interact. The males would hold infants for hours at a time, occasionally taking them back to their mothers for feedings. By using behavioral observations, social network analysis, and measures of fecal glucocorticoid metabolites (indicator of physiological stress) and comparing these to various seasons (spring birth season and autumn season) the authors were able to tease apart some of these male social behaviors. The hypothesis was that the infants would calm the males. However, analysis of hormone levels showed that stress hormones increased, suggesting that the males carried the infants to show that they could handle the pressure. Social network analysis showed that those males who carried infants was not related to rank, and that infant-carriers had stronger ties with other males when compared with non-infant-carriers.

Who knew that males macaques were such suckers for babies? I guess those furry, pink, wrinkly faces are kinda cute.

Here's the paper:
Henkela, Stefanie, Michael Heistermannb and Julia Fischer (2010) Infants as costly social tools in male Barbary macaque networks. Animal Behaviour: 79 (6), 1199-1204. (DOI: 10.1016/j.anbehav.2010.02.005)
and here's a great article in The New York Times:
http://www.nytimes.com/2010/06/15/science/15fath.html

Sneaky Males

The boy-meets-girl scenario is not always so simple in nature. Often it is the boy-must-convince-girl and/or boy-must-keep-girl scenario. Many males pick flashy coloration, elaborate dancing, amazing architecture, gift-giving, feats of courage, and cautious mate guarding. This particular story is one of deception, antelope deception that is.

Many antelope mating systems are set up so that a male maintains a territory and females who like a territory will stay there to feed and likely mate with the male of that territory. And so, the higher quality the territory the more likely that a female, or many females, will mate with that particular male. That's the plan anyway.

In the case of the topi antelope, males have found a loophole in the system. Topi antelope females are only in heat for one day per year, and they generally visit multiple territories, mating with resident males during that time. So if you are a male topi antelope you want to keep females in your territory as long as possible to increase the likelihood that you are the father of the most antelope babies. How do you accomplish this? When a female is appearing to leave his territory the male runs in front of her, freezes, stares in the directions she is going, and starts snorting loudly. This is typically a behavior exhibited by animals who detect a predator (a cheetah, lion, leopard, or whatever) -- an alarm snort, if you will. The female then retreats back into the territory. In this case its all a big show, further evidenced by the fact that the male attempts to mate with the female right after the curtain falls. The male is pretending to sense a predator so that the female will stay in his territory. This study, published online in The American Naturalist, is the first case to find males duping females in this way. This is a pretty ingenious and relatively rare behavior, considering it is energetically efficient, safe for the male, and it works because ignoring a predator-alert signal could potentially be fatal.

Bro‐Jørgensen and Pangle, the authors of the paper, tracked 74 female topis in estrus through the years 2005-2009. They observed the females as they visited the territories of various males. They also observed the males in the absence of females. They observed this fake-alarm-sound behavior and found that the females almost always fell for it.

They also recorded the sounds made by males and found that they could be classified into three categories: a real alarm sound, a false alarm sound, and a regular grunt or snort. When they played these recorded sounds to 60 different females they observed that the females ignored the regular grunts but froze in place at the real and fake snorts. This suggests that the sound itself (excluding the visual, body language signals) is close enough that real and fake are indistinguishable to the females.

Smooth, very smooth.

Jakob Bro‐Jørgensen and Wiline M. Pangle. (2010) Male Topi Antelopes Alarm Snort Deceptively to Retain Females for Mating. The American Naturalist: 176, published online. (DOI: 10.1086/653078)

Here are a couple of write-ups about the article:
http://www.nytimes.com/2010/05/25/science/25obantelope.html?ref=science#
and
http://www.time.com/time/health/article/0,8599,1991425,00.html

(image from http://newsimg.bbc.co.uk)