Lemur habitat was changing before humans even arrived

New research from the DNA of mouse lemurs (of the genus Microcebus) has lead to a surprising discovery about Malagasy forests and their ancient past. Madagascar, a large island off the west coast of Africa, is made up of many forests that are presently not connected and haven't been since around the time humans reached the island. The eastern rainforests (green in the image below) are separated from the western, deciduous forests (blue in the image below) by an expanse of grasslands (in yellow). There are multiple theories concerning what the landscape looked liked in the past and why the eastern and western forests are separated, and research from Yoder and colleagues (2016) uses the genetic history of lemurs to tell us more.

Habitats of Madagascar and species locations. 

From Yoder et al., 2016

Some believe that, rather than this disconnect we now see between western and eastern forests, Madagascar was covered in closed-canopy forests prior to the arrival of humans, with humans acting as the primary agents of change. This so-called forest hypothesis maintains that the large expanse of grasslands that experience frequent burning were once forests and their reduction was not natural.Others believe that the grasslands we see today are similar to ancient grasslands found in Madagascar. Thus, the landscape was not so radically different from the present. This is referred to as the grassland hypothesis by Yoder and colleagues (2016). Finally, another idea termed the mosaic hypothesis by Yoder and colleagues (2016) suggests that the central part of the country was covered with a mix of wooded savanna and closed-canopy forests.


Some of the world's top lemur experts have provided us with new information on the history of Madagascar's forests. Yoder and colleagues (2016) looked at the DNA of five different species of mouse lemurs, a genus dependent on the forest, to understand how the forests across this island nation changed. One of their research questions asks if the divide between the two forest habitats is natural or what remains of a transitional cline?

Results suggest that the five species studied started diverging from one another roughly five hundred and forty thousand years ago with the last node of divergence around fifty-five thousand years ago. The timing of mouse lemur evolution and divergence coincides with evidence suggesting great variation in climate.

M. murinus. Photo: Joachim S. Muller

Genetic analysis of M. myoxinus, a subspecies of mouse lemur that lives in continuous forests, and M. lehilahytsara, another subspecies that lives in a mosaic of forests, show significantly different patterns in regards to geographic patterns of divergence. Results suggest that M. lehilahytsara, the mouse lemur in a mosaic of forests, has lived in this type of habitat for a very long period of time, since before the arrival of humans. Thus, genetic evidence from mouse lemurs does not support the forest hypothesis.

Yoder and colleagues (2016) also discovered that  M. berthae and M. rufus are more closely related than would be expected, given their geographic differences. One species lives lives in the southeast in humid forests and the other in dry forests of the west. This close genetic relationship points towards the mosaic hypothesis of Madagascar's ancient geography. We see a genetic divergence that is tens of thousands of years old and not uniform across all Microcebus species.

Thus, using the genes of mouse lemurs, Yoder and colleagues (2016) were able to conclude that the central part of Madagascar was composed of a mosaic habitat composed of forests and grasslands. The arrival of humans does not appear to have caused a tremendous change from an entirely forested landscape to grasslands similar to what we see today.


Links of possible interest:

Ecosystems in Madagascar
Read the paper here
They may be cute, but you shouldn't have a primate as a pet


Works cited: 

Blome, M. W., Cohen, A. S., Tryon, C. A., Brooks, A. S., & Russell, J. (2012). The environmental context for the origins of modern human diversity: a synthesis of regional variability in African climate 150,000–30,000 years ago. Journal of Human Evolution, 62(5), 563-592.
Cannon, C. H., Morley, R. J., & Bush, A. B. (2009). The current refugial rainforests of Sundaland are unrepresentative of their biogeographic past and highly vulnerable to disturbance. Proceedings of the National Academy of Sciences, 106(27), 11188-11193.
Scholz, C. A., Cohen, A. S., Johnson, T. C., King, J., Talbot, M. R., & Brown, E. T. (2011). Scientific drilling in the Great Rift Valley: the 2005 Lake Malawi Scientific Drilling Project—an overview of the past 145,000 years of climate variability in Southern Hemisphere East Africa. Palaeogeography, Palaeoclimatology, Palaeoecology, 303(1), 3-19.
Yoder, A. D., Campbell, C. R., Blanco, M. B., dos Reis, M., Ganzhorn, J. U., Goodman, S. M., ... & Ralison, J. M. (2016). Geogenetic patterns in mouse lemurs (genus Microcebus) reveal the ghosts of Madagascar's forests past. Proceedings of the National Academy of Sciences, 201601081.

The spatial and temporal complexity of fruit species consumed by chimps

Chimpanzees live in a variety of environments, thus the types of food they consume vary accordingly. We wouldn't expect a chimpanzee troop living in Fongoli (a savanna) to consume the same foods as chimpanzees living in Gombe (a tropical forest).

That caveat aside, chimpanzees across habitats prefer fruits to other food types. We know this because fruits make up a greater proportion of their diet than would be expected given fruit availability (Hladik, 1977; Tutin et al., 1997; Conklin-Brittain et al., 1998; Wrangham et al., 1998; Doran-Sheehy et al., 2006). Fruits are high in energy and low in secondary compounds, or digestive inhibitors or toxins, such as tannins or lignin. (Remember that the fruits we see in a grocery store or at a food stand have been selectively bred to look and taste considerably different than most wild fruits). Interestingly, chimpanzees in Guinea-Bissau consume mainly wild fruits and flowers even when they are in close proximity to agricultural areas (Carvalho et al., 2015). Thus, it seems safe to conclude that fruits are high up on the desired menu.

Feeding on Ficus sur fruits, Photo credit: Alain Houle

A recent study by Janmaat and colleagues (2016) looked at three populations of chimpanzees in tropical lowland rainforest, lowland tropical moist forest, and a moist evergreen tropical forest to better understand how chimpanzees access energy-rich foods. They considered multiple food types that are high-energy: young leaves, unripe fruit, and ripe fruit. The authors also had a particular interest in large crops of ripe fruit. They described the probability of finding trees for each of the aforementioned, three food types and how predictable ripe fruit production is in each focal tree in regards to timing, frequency, and quantity of ripe fruit produced. 

 The authors found that individuals were more likely to encounter young leaves or unripe fruit than ripe fruit, confirming that fruits present more of a challenge than other food types. However, over half of all of the trees chimpanzees encountered over the course of this study were species of fruiting trees consumed by chimps. Thus, finding a tree species known to produce an edible fruit isn't a monumental challenge for these populations. The challenge lies in timing.  

There was considerable variation in the timing of fruit production within a population of a tree species. Within the same species, the length of fruit production varied: one individual may produce fruit for a few months over multiple years whereas another individual may fruit for many more months within the same period. There was also monthly variation in the size of fruit crops produced. Further variation within a species complicates matters for chimps even more, as they can't count on large crops of fruits in certain months, even within individual species.

Look for an upcoming post on the implications of finding ripe fruits in a complex environment. How might the ecology of chimpanzee habitat and their dietary choices affect their intelligence?

Links of potential interest:
Chimps understand and choose to cook
Female chimpanzees more likely to use tools when hunting than males
 

Works cited:

Carvalho, J. S., Vicente, L., & Marques, T. A. (2015). Chimpanzee (Pan troglodytes verus) Diet Composition and Food Availability in a Human-Modified Landscape at Lagoas de Cufada Natural Park, Guinea-Bissau. International Journal of Primatology, 36(4), 802-822. 

Conklin-Brittain, N. L., Wrangham, R. W., & Hunt, K. D. (1998). Dietary response of chimpanzees and cercopithecines to seasonal variation in fruit abundance. II. Macronutrients. International Journal of Primatology, 19(6), 971-998.

Doran-Sheehy, D. M., Shah, N. F., & Heimbauer, L. A. (2006). Sympatric western gorilla and mangabey diet: re-examination of ape and monkey foraging strategies. Cambridge Studies in Biological and Evolutionary Anthropology, 48, 49.

Hladik, C. M. (1977). Chimpanzees of Gabon and chimpanzees of Gombe: some comparative data on the diet. Primate Ecology: Studies of Feeding and Ranging behaviour in Lemurs, Monkeys, and Apes, 81-501.

Janmaat, K. R., Boesch, C., Byrne, R., Chapman, C. A., Bi, G., Zoro, B., ... & Polansky, L. (2016). Spatio‐temporal complexity of chimpanzee food: How cognitive adaptations can counteract the ephemeral nature of ripe fruit. American Journal of Primatology.

Tutin, C. E., Ham, R. M., White, L. J., & Harrison, M. J. (1997). The primate community of the Lopé Reserve, Gabon: diets, responses to fruit scarcity, and effects on biomass. American Journal of Primatology, 42(1), 1-24.

Wrangham, R. W., Conklin-Brittain, N. L., & Hunt, K. D. (1998). Dietary response of chimpanzees and cercopithecines to seasonal variation in fruit abundance. I. Antifeedants. International Journal of Primatology, 19(6), 949-970.

Another primate "sleeps" away hard times

Hibernation allows an organism to lower its metabolism, heart rate, body temperature, and breathing in order to expend less energy during what may be a difficult time, such as a cold winter.  Hibernation is a tactic commonly associated with rodents and polar bears but primates do it too. The fat-tailed dwarf lemur (Cheirogaleus medius) on the island of Madagascar hibernates during the dry season, using the fat in its tail to survive the winter. The Crossley's dwarf lemur (Cheirogaleus crossleyi) and the Sibree's dwarf lemur (Cheirogaleus sibreei) also hibernate. Some primates (Microcebus murinus, Allocebus trichotis, Galago moholi, and others) will enter what is called torpor, during which body temperature and metabolism is lowered but for a period less than 24 hours. Lemurs were thought to be the only primate that hibernated, until a close cousin changed the game.

Pygmy slow loris. Photo: David Haring at Duke Lemur Center

It has recently been reported that the pygmy slow loris (Nycticebus pygmaeus), a nocturnal primate living in Cambodia, China, Laos, and Vietnam does in fact hibernate (Ruf et al., 2015). The authors behind this study set out to find a hibernating primate outside of Madagascar and they succeeded.

Ruf and colleagues found it hard to believe that hibernation in primates would be restricted to only Madagascar, so they started thinking about what environmental conditions and physical characteristics would make an animal likely to hibernate. They hypothesized that a hibernating primate would be small, as most hibernating animals are (Ruf and Geiser, 2015), that the animal would live in an environment that is distinctly seasonal in temperatures and/or precipitation, and in an environment with seasonal changes in food availability. Given the primates known to use torpor, primates falling into the suborder Strepsirrhines seemed like their best bet.

The pygmy slow loris fit their criteria. It was logical that a small primate facing cold temperatures in winter and low food availability would adapt using hibernation. Thus lowering energy requirements during a period of limited resources. While previous descriptions of the pygmy slow loris were in accord with hibernation (Ratajszczak, 1998; Streicher, 2005), no measurements had been taken. Thus, Ruf and colleagues decided to take some.

After measuring temperature (but not metabolic rate) in five adults over 769 days total, animals hibernated for several days during midwinter interspersed with periods of activity and or torpor. On average, animals hibernated for 43 hours (± 3 hours with a range of 25.9-62.6 hours).

Thus, evolutionary mechanisms have not limited hibernation in primates to Madagascar. As more research is done, it is possible that hibernation will be found in other primate species inhabiting seasonal environments.

Links of possible interest:
Discovery of hibernation in fat-tailed dwarf lemur
Primate hibernation more common than previously thought
The costs and benefits of hibernation

Sources:

Ratajszczak, R. (1998). Taxonomy, distribution and status of the lesser slow loris Nycticebus pygmaeus and their implications for captive management. Folia Primatologica, 69(Suppl. 1), 171-174.

Ruf, T., Streicher, U., Stalder, G. L., Nadler, T., & Walzer, C. (2015). Hibernation in the pygmy slow loris (Nycticebus pygmaeus): multiday torpor in primates is not restricted to Madagascar. Scientific reports, 5.

Ruf, T. & Geiser, F. Daily torpor and hibernation in birds and mammals. Biol. Rev. 90, 891–926, doi: 10.1111/brv.12137 (2015).

Streicher, U. (2005). Seasonal body weight changes in pygmy lorises Nycticebus pygmaeus. Verhandlungsber. Zootierkrk, 42, 144-145.

Studying the ecology of disease and primates

We often think of habitat loss, hunting, and perhaps even the pet trade as serious threats to primate conservation. Disease, on the other hand, is commonly forgotten. Yet, increasingly fragmented forests create more opportunities for humans and wildlife to come into contact and potentially transfer and spread disease. Our close genetic relationship with non-human primates further increases the likelihood of spreading illness through contact, making this a topic worth paying attention to.

Cryptosporidium parvum

A study came out recently in the journal PLOS Neglected Tropical Diseases that should remind all of us not to exclude disease as a potential threat to non-human primate conservation. Parsons et al., 2015 studied chimpanzees (Pan troglodytes) and baboons (Papio anubis) in Gombe National Park (where Jane Goodall studied chimps) and found that they are exposed to a parasite called Cryptosporidium. Cryptosporidium is transmitted through food, water, and zoonotic means (from animals to humans).

Death from infectious disease is the leading cause of mortality for the three chimpanzee communities inhabiting Gombe (Lonsdorf et al., 2006; Williams et al., 2008), thus studying disease ecology should allow us to better conserve the Gombe population. While Papio anubis is not endangered, Pan troglodytes is.

Of the 131 non-human primates tested, 16% were positive for Cryptosporidium compared to 9.6% of livestock and just 4.3% of the 185 humans tested. Baboons and chimpanzees were infected at a similar rate. Three species of Cryptosporidium were detected: C. hominis, C. suis, and C. xiaoi.
 

Bush pig, Photo credit: Derek Keats

Half of the Cryptosporidium documented in the Kasekela community of chimpanzees are of a Cryptosporidium species (C. suis) typically associated with pigs. Surprisingly, C. suis was not detected in any of the humans, baboons, or livestock tested. The authors suggest that the transmission cycle may involve bush pigs, Potaochoerus larvatus, because domesticated pigs are not present in this area due to a mainly Muslim population. The bush pigs are found in the forest the Kasekela chimps inhabit and may serve as a reservoir for the parasite. It seems there are more details to be teased out when understanding the connection between C. suis and humans. Another species of the Cryptosporidium parasite found in this study, C. hominis, is one of two species most commonly found in humans (Chalmers and Katzer, 2013; Insulander et al., 2013). Yet C. hominis was also found in baboons and one of the chimpanzee communities, raising a red flag.

Cryptosporidium has been found in other primate species as well, including mountain gorillas, which were found to have the same species of Cryptosporidium, C. parvum, as found in nearby human populations (Nizeyi et al., 1999; Graczyk et al., 2001). Cryptosporidium has also been reported in red colobus and black and white colobus monkeys (Sayler et al., 2012). The Parsons study thus contributes to a growing body of literature on the prevalence of zoonotic diseases and their transmission. The authors stress the need to further understand the complex connections between primates, their ecology, their contact with humans, and the spread of disease so that we can better understand this relatively unexplored area of primate conservation.

This is an interesting article because Parsons and colleagues tackled a question that is poorly studied. The ecology of how diseases like Cryptosporidium spread and affect our primate relatives is not well understood, but zoonotic diseases make up the majority (60.3%) of emerging diseases worldwide (Jones et al., 2008). This is a timely and interesting paper that is worth reading or at least skimming. You can find the article posted online here. It's free and worth a look!

Links of interest:
Non-human primate biosafety from the University of Minnesota
Studying disease emergence in primates may help us understand emergence in humans
ScienceDaily article on paper


Sources:

Chalmers, Rachel M., and Frank Katzer. "Looking for Cryptosporidium: the application of advances in detection and diagnosis." Trends in parasitology 29.5 (2013): 237-251.

Insulander, M., et al. "Molecular epidemiology and clinical manifestations of human cryptosporidiosis in Sweden." Epidemiology and infection 141.05 (2013): 1009-1020.

Jones KE, Patel NG, Levy MA, Storeygard A, Balk D, et al. (2008) Global trends in emerging infectious diseases. Nature 451: 990–993 doi: 10.1038/nature06536
Graczyk TK, DaSilva AJ, Cranfield MR, Nizeyi JB, Kalema G, et al. (2001) Cryptosporidium parvum Genotype 2 infections in free-ranging mountain gorillas (Gorilla gorilla beringei) of the Bwindi Impenetrable National Park, Uganda. Parasitology Research 87: 368–370. pmid:11403378 doi: 10.1007/s004360000337 

Lonsdorf EV, Travis D, Pusey AE, Goodall J (2006) Using retrospective health data from the Gombe chimpanzee study to inform future monitoring efforts. American Journal of Primatology 68: 897–908 

Parsons, M. B., et al. "Epidemiology and Molecular Characterization of Cryptosporidium spp." Humans, Wild Primates, and Domesticated Animals in the Greater Gombe Ecosystem, Tanzania. PLoS Negl Trop Dis 9.2 (2015): e0003529.

Nizeyi JB, Mwebe R, Nanteza A, Cranfield MR, Kalema G, et al. (1999) Cryptosporidium sp and Giardia sp infections in mountain gorillas (Gorilla gorilla beringei) of the Bwindi Impenetrable National Park, Uganda. Journal of Parasitology 85: 1084–1088. pmid:10647041 doi: 10.2307/3285672 
Salyer SJ, Gillespie TR, Rwego IB, Chapman CA, Goldberg TL (2012) Epidemiology and Molecular Relationships of Cryptosporidium spp. in People, Primates, and Livestock from Western Uganda. Plos Neglected Tropical Diseases 6.(4):e1597. doi: 10.1371/journal.pntd.0001597. pmid:22506085

Williams JM, Lonsdorf EV, Wilson ML, Schumacher-Stankey J, Goodall J, et al. (2008) Causes of death in the Kasekela chimpanzees of Gombe National Park, Tanzania. American Journal of Primatology 70: 766–777 doi: 10.1002/ajp.20573

What is a keystone species?

A keystone species is any species that plays a critical role in how the ecosystem functions. Couldn't one argue that every species is a keystone species, playing an important role? Well, a keystone species plays a disproportionately large role in maintaining the ecosystem structure and function.

Sea otters are a great example of a keystone species

For example, let's look at sea otters. They're a common example of a keystone species. Why? Well, because they feed on urchins. Urchins feed on kelp. By preying on the urchin population, sea otters prevent urchins from consuming too much kelp. Kelp forests are home to many species, including invertebrates, fish, and marine mammals. In addition to being important habitat, lots of other animals feed in the kelp forests, such as seals and sea lions. Kelp forests can be destroyed by urchins, but the sea otters feed on urchins, preventing this from happening. Without the sea otters to feed on the urchin, the urchin might consume massive amounts of kelp, destroying important habitat feeding waters for other animals. So the effect of this one species on the ecosystem is very large, larger than one would expect for a single species.

Many predators function as keystone species, limiting the population growth of multiple omnivores/herbivores. Wolves eat deer and deer eat small trees, so wolves protect this new growth. Jaguars, tiger sharks, mountain lions and sea stars are all predators that function as keystone species.

Pacific salmon is another good example of a keystone species and not because of what this species does during its life but because its death is so important. The salmon life cycle involves salmon returning to the freshwater streams they were born in to spawn (males release sperm and females release ova into the water) and then die. Like anything that's dead, the salmon then decompose in these waters. Their death provides a significant amount of nitrogen to the watershed (the area of land where all of the rain or water under the land drains to, click here for more info).  Salmon runs, when salmon return to the freshwater they were born in and spawn themselves, provide a crucial source of nutrients to areas that otherwise might have low productivity, and they act as a food source for many animals, including grizzlies and eagles.

Red mangroves

But let's not forget our green friends. Plants can function as keystone species too. Red mangroves, Rhizophora mangle, are found at the edge of the water. Their roots act as a nursery to fish and crustaceans. Red mangroves provide habitat for many species, such as manatees, birds, and fish, They protect against erosion and act as buffers from large waves, literally structuring the land around them by preventing soil erosion and acting as anchors.

The concept of a keystone species was first introduced by Robert Paine in 1969, who studied sea stars and noticed that removing this key predator had cascading effects. Since Paine's work, we've come to realize the importance keystone species have in their communities. These important species are often targets for conservation efforts, as conserving them protects many species and ecosystems.

Food for thought: Do some research on the reintroduction of wolves to Yellowstone National Park. How did the arrival of wolves in 1995 change Yellowstone? How is this example of a keystone species connected to conservation in Yellowstone?

If you want to learn more, check out this great resource from Nature: Keystone Species.

What is an ecological niche?

What is an ecological niche? This is a question you'll probably encounter if you study primatology/ecology/zoology/etc. If I search for "niche" in the dictionary that comes with my Mac, I find that niche is "a position or role taken by a kind of organism within its community."  But what does that mean? Niche is a concept I found some students in the introduction to anthropology course struggled with, so let's take a closer look.

Some factors that contribute to niche

A niche is more than just the environment an organism lives in, it really is the role the organism takes (so the dictionary definition isn't entirely bad). It's not just where an animal lives, but the animal's behavior, what time of day its active in its environment, what foods it prefers most to eat, what foods it can eat when preferred foods aren't available, and so forth. How an animal responds to resources is part of its niche as is how it may respond to any predators. An animal's life history, or the sequence of events from birth to death related to reproduction, is also part of its niche. Many animals occupy the same environment. You could sit very, very quietly in a tropical forest for a couple of hours and see multiple animals exploiting a single fruiting tree.

If we just talk about primates for a minute, we may find one species of primate eats leaves from this tree. A second primate species consumes the ripe fruit on the tree during the day. A third species of primate ignores the fruit entirely, is only active at night, and instead hunts for insects and small reptiles on this tree.

Fundamental vs realized niche

This is an over simplified example though because a niche really is more than just diet or just habitat. Niches are complex. The actual or realized niche of a species may very well be entirely different from its fundamental niche, or the entire role/area a species could utilize in its niche if free from limitations. For example, while a primate that lives mainly on leaves may love to eat fruit, other competitors may prevent that primate from doing so. Thus, the realized niche does not include fruit but the fundamental niche does, because the primate is capable of foraging and feeding on that fruit. Keeping in mind the difference between realized and fundamental niche, different populations of the same species may have different realized niches. Let's say there are two populations of the same primate species but they live in slightly different patches of forest. Depending on the predators and conditions in each of those two forests, the same species may be able to exploit resources differently or have slightly different behavioral patterns because of lower predation rates in one forest compared to the other. Thus, the realized niches might differ.


Food for thought: I'd say humans have one of the most flexible and largest ecological niches of all species. Would you agree?

Here's a cool article about the first visualization of an ecological niche. Check it out!

Invasion of the fittest

Berenty Private Reserve is primarily a tourist site. The concern is with ensuring tourists have an enjoyable stay and see lots of lemurs right outside of their cabins. The few researchers who come to Berenty to work must contend with this fact.

Invasive vine that has been very successful

One of the problems that arise from Berenty being a tourist facility is the number of invasive species present here. Invasive species can take root anywhere, not just tourist sites. In Florida, work is being done to eradicate a species of land snail originally from Africa that can grow as large as a rat. The snail is thought to have been introduced by a religious group using the snail for ritual purposes. Asian carp were introduced on purpose in the Great Lakes to reduce algae levels. It turns out they eat pretty much anything and are completing taking over the Great Lakes and drastically reducing biodiversity.

Here at Berenty, certain plants have been planted for aesthetic pleasure. For example a row of cactus was planted along the road and the edge of the forest. This seems perfectly harmless at first glance. However, the inclusion of this plant in the ecosystem does change things. Lemurs eat the cactus, birds eat it, and before you know it you have cactus popping up in the forest itself. Cactus is popping up where it shouldn’t be and where it doesn’t belong. The same is true for other plant species brought in for aesthetic pleasure: they spread everywhere and find their way into the forest. These invasive species may be more successful than native species, driving out the original inhabitants and causing extinction of native species.

At least two of my three sifaka groups that I study I’ve seen eat from a species not native to this habitat. I’m doubtful it will affect my research, because I am looking to see if there are any differences between the sexes in their feeding habits. Invasive species certainly affects any researchers who come here to study diet. In fact, because of the introduced plant species and the provisioning of primates with human food that occurs at Berenty, this site could not really be used to study natural primate diet.

With the world growing smaller, humans travelling globally inadvertently bring seeds and invasive species with them. Primates and humans increasingly come into contact. Questions concerning primate diet in unnatural, altered ecosystems may be all that scientists are able to ask.

Island living

Madagascar is the world’s fourth largest island. It is thought to have reached its present day location in relation to the African continent about 130 million years ago. Today, 400km separate Madagascar from the rest of Africa. Lemuriformes are though to have colonized Madagascar roughly around 65 million years ago, so how did the ancestors of sifakas, ring-tailed lemurs, and others arrive on the island? Are lemurs great endurance swimmers? Not exactly.

Madagascar's hissing cockroaches

What determines whether a species colonizes an island? Is colonization of an island something scientists can predict? The principles of island biogeography lend us a hand in determining whether or not an island will be successfully colonized by new species.

For starters, the closer the island is to the mainland or another large land mass, the more likely that island is to be colonized. The older the island is the more likely the island is to be colonized. The larger the island is the more species are likely to colonize it. All of these fancy rules are pretty simple once you think about them. The older the island is, the more time has passed, allowing species to reach the island. The larger the island is, the more space there is for all of those new species. And the closer the island is to other landmasses, the less distance between the two landmasses makes for an easier crossing for new species.

In terms of the genetics behind island biogeography, the following rules apply. As time passes and the island has been settled by those species that were able to the island and been successfully live there, genes are less likely to be exchanged between the original population from the mainland and the population on the island. As even more time passes, the two populations become genetically different.

Ancestral lemurs likely reached Madagascar by a series of rafts. This would have occurred not over a summer holiday but over an extended period of time in a series of events. As time passed, ancestral lemurs diverged from their original population and became genetically distinct. They thrived on the island of Madagascar and became the species we know today.

Primate diet

Primates can be grouped into categories based on what their diet is primarily composed of. Primates that eat mostly leaves are called folivores. Primates that eat mostly fruit are called frugivores, mostly gums=gumivores, mostly insects=insectivores, and mostly meat=carnivores. There is only one solely carnivorous primate, the tarsier. This small Asian primate eats insects, lizards, and even small mammals. Tarsiers are solitary and nocturnal primates that truly eat nothing but meat.

Crocodile at Berenty  (in enclosure)

Sifakas are folivores. Think about the last time you ate a salad with only lettuce and other leaves. If you’ve ever attempted such a bland meal, was it filling? Probably not. Leaves aren’t exactly the most high-energy food item, so a lot of leaves need to be ingested if that’s going to be your diet. Leaves can also be hard to digest because they contain cellulose (it’s part of the plant cell wall and is what humans call “dietary fiber” in our diets). Some leaves may even harbor toxins that protect the leaves. Sifakas and other folivores have adaptations to handle these difficulties. They have a longer digestive tract than we do and they likely have behavioral adaptations as well. Leaves are low energy, and sifakas are low energy primates. Like many folivores, they do not spend a lot of time engaged in social activities. Rather, sifakas spend significant portions of their day just resting, conserving energy, and digesting their food. (They’re not the most interesting primates to do behavioral observations on, but they’ll suffice for my research questions.)

Sifakas feeding on flower buds

Now, just because we may call a sifaka a folivore does not mean that this species only eats leaves. Many species of primates consume a variety of food items dependant on availability. Gorillas are often classified as folivores for example, but they certainly feast on fruit when it is available. Diet composition can vary within a species too, if the species inhabits multiple habitats with differing food availability.

Critical thinking: Howmight a carnivore’s activity pattern differ from a folivore’s activity pattern? What other variables need to be considered?

Critical thinking: How might introduced plant species or other food sources introduced through humans affect a primate? Think about group size, aggression, infant mortality rates: would these increase or decrease?