Yes, exactly, but I thought large canines and the threat display thing in apes was more about social structure, especially male/male competition, and particularly in societies with just one to a few adult males and several adult females. And gibbons tend to live in pair-bonds instead, though I think they are highly territorial, so I suppose that’s the missing part for me.
tl;dr help I don’t know what primates do when they’re still alive.
Ok, so I’ve been fighting with my online journals all day today (for some reason I can log in but it says I’m not subscribed to any journal. UGH!) so I’m going to have to come back to this in a few days once everything is sorted. I’ll give you a quick-ish and dirty answer for now though…
So when it comes selection forces for a particular structure or behavior (or combination thereof) there are a few things we need to consider; I call them the three F’s…
What kind of foraging does this animal do? Are they a specialist or generalist? What various foods make up their diet? I mean, sure, you all know canines would be helpful for hunting and killing another animal (look at our carnivore friends), but what about insects that live in difficult to access hives/nests? Gum which must be scraped off the nodes of acacia trees? Fruit or nuts which are difficult to crack?
Teeth must be appropriately suited to the diet of each species. If you’re hunting and killing prey, large canines make great weapons. If you’re foraging for difficult to access insect or plant matter that requires a lot of scraping and biting, large teeth may also be beneficial. This is just one piece of the puzzle…
Fight for access to mates, fight to run off other groups (and other species), fight do defend / escape from predators…. etc. etc. There’s a lot of fighting going on in the animal world and large canines make excellent weapons. Most primates don’t have true claws (the exceptions here being the Aye-aye and members of the Callitrichidae sub-family), so teeth are basically all we have as far as weapons. Well… teeth, brains, and being social (friends to back you up is always a good thing).
But of course every altercation doesn’t end in a fight to the death. A lot of times you just have to show what you’re working with (be it teeth, body size / strength, vocalizations, etc) and your opponent will back off.
(Patas monkeys use their long canines in yawn displays to ward off / threaten other individuals…. and for acacia gum scraping like the Vervet above)
Depending on the social / mating structure of a species, individuals will develop a particular fighting (or competition) style. How often you need to fight / defend yourself, from individuals both in and outside of your own species, will play a huge role in how big your weaponry needs to be.
Ok, so I know I mentioned fighting for access to mates above, but what about mate choice? Some females like males with exaggerated display characteristics (why else would Chlorocebus and Erythrocebus have blue testicles!) and others prefer a more neotenic (literally meaning child-like) driven image. Think about humans with our reduced facial / body hair, flat faces, large domed foreheads… we’re basically big babies. Now I’m not saying every primate is like this (goodness no), but mate choice has a huge effect on shaping morphological and behavioral characteristics.
So we have to consider (at least) all three of these things when looking into possible selection forces for the evolution of a certain behavior or trait.
Gibbons do have intra and interspecies fights, but majority of their territory defense is vocally. They mate for life, although extra-pair copulations occur (you sneaky fuckers you), so mate guarding / competition isn’t as pronounced as primates in a harem or multi-male/ multi-female group would be… so unsurprisingly their canines are not sexually dimporhic. (x, x) BUT gibbons are a predominantly frugiviorous. They eat a huge variety of different fruits, vines, leaves, woody plants, flowers, insects, and figs. Lots and LOTs of figs. (x)
I would say that the gibbon canine size was selected for because of a combination of all three of these things. Females found these males attractive (or at least not unattractive), males and females with these developed canines were more capable at defending themselves during physical confrontations, and it helps when foraging through the tough skins of fruits and other foraging matter (video).
I included a few links within, but I’ll update and reblog this post with sources once I get this journal access mess cleared up.
tl;dr - Nothing is ever a simple answer when it comes to Ethology
Darlin, you’re the BEST. I pulled a gibbon skull out of the drawer on Friday, saw his canines, and was like ‘how the HECK am I going to explain this if my Intro to Bioanth kids ever find out that gibbons have these teeth?!’*
(*I am likely overestimating my students’ drive to both look up gibbon canines and the curiosity to ask me about them BUT STILL)
Western lowland gorilla © Steffen Schmidt / EPA
Rescue bid launched to save Hainan gibbon from becoming first ape driven to extinction by humans.
- by Daniel Cressey
“China’s wildlife conservation efforts are under scrutiny as scientists battle to save a species found only in a tiny corner of an island in the South China Sea. The Hainan gibbon is the world’s rarest primate and its long-term survival is in jeopardy, according to an analysis.
Only 23 to 25 of the animals are thought to remain, clustered in less than 20 square kilometres of forest in China’s Hainan Island. The species (Nomascus hainanus), which numbered more than 2,000 in the late 1950s, has been devastated through the destruction of habitat from logging, and by poaching. Extinction would give the gibbon the unwelcome distinction of being the first ape to be wiped out because of human actions. To hammer out a plan to save it, international primate researchers convened an emergency summit in Hainan last month.
“With the right conservation management, it is still possible to conserve and recover the Hainan gibbon population,” says meeting co-chair Samuel Turvey, who studies animal extinctions at the Zoological Society of London (ZSL). “But given the current highly perilous state of the species, we cannot afford to wait any longer before initiating a more proactive and coordinated recovery programme.” He adds that the meeting was a successful first step towards saving the animal and that a plan of action is being finalized.
The plan will be based in part on a ‘population viability analysis’ that models the potential size of the gibbon population in coming decades for a range of different scenarios. It is being drawn up by Kathy Traylor Holzer, a conservation planner at the Conservation Breeding Specialist Group in Apple Valley, Minnesota. “It’s one of the smallest populations I’ve ever worked with,” says Traylor Holzer. “That number — in one place — is extremely scary.”
Preliminary modelling, which considers factors such as breeding success, habitat changes and natural threats, suggests that the Hainan gibbon may be safe from extinction in the next couple of decades. But its restricted habitat means that a single catastrophic event, such as a typhoon or a disease outbreak, could wipe out the minuscule population. Furthermore, low genetic diversity in the remaining animals could result in unhealthy offspring because of inbreeding. To better understand the genetics of the animals, ZSL researchers are conducting DNA sequencing using collected faeces" (read more).
Mammal Monday, Tarsier. Tarsiers are small animals with enormous eyes; each eyeball is approximately 16 mm.
© The Field Museum, Z84060, Photographer Catherine Hoogstraal Walker.
One of the tarsiers that lived at the Brookfield Zoo.
A star is born!
At 6:30 pm on Thursday, March 13, Imani, an 18 year-old Gorilla at the San Diego Zoo Safari Park, gave birth to a baby girl via emergency C-Section. Neonatologist Dawn Reeves of UC San Diego Health System was on hand to aid the team with this very special delivery.
Pictured above are Dr. Reeves and Caitlin Forrest, one of our NICU nurses, with Imani’s baby very soon after her birth.
This little baby melted the hearts of all who cared for her and, despite a few early complications, Imani has successfully reunited with her baby and introduced her to the troop.
A happy ending, indeed!
I’m tellin you,
You better watch your step
You’ll fall and hurt yourself one day
Baby listen, you better watch step
You’ll fall and hurt yourself one day
(Anita Baker - Watch Your Step)
Chimpanzees who have positive experiences with humans relate to humans more than unfamiliar chimps and baboons!
Chimps put people ahead of baboons
- Jennifer Viegas, Discovery News
Chimpanzees that have had positive experiences with humans appear to trust people more than they do baboons and unfamiliar chimps, a new study suggests.
The findings, published in the latest Proceedings of the Royal Society B, indicate that chimpanzees can learn to bond and exhibit empathy for members of another species, such that trust develops even at the subconscious level.
As for what chimps think of kind and caring humans, lead author Dr Matthew Campbell says, "I have no doubt that we are different in their minds, but an okay kind of different."
Campbell, a researcher at the Yerkes National Primate Research Centre, says an older female chimp named Tai is so pleased to see co-author Dr Frans de Waal, whom she’s known for 20 years, that she excitedly pants, bobs her head and stretches out her hand.
All of these are behaviours chimps use when greeting each other.
For the study, Campbell and de Waal used contagious yawning to measure “involuntary empathy” among 19 adult chimps at Yerkes that were all raised by other chimps in captivity.
"We think the mechanism for copying the yawns of others is the same for copying other facial expressions, like happiness, sadness or fear," he explains.
"For our purposes, yawning is simply a contagious expression we can easily see and count. Contagious smiles, frowns and fearful expressions may be tiny twitches of muscles that cannot be seen, but yawns can’t be missed.
"We catch all of these expressions more, the closer we feel to someone, and that’s why we think that empathy is involved." (continue reading)
Campbell, Matthew W., and Frans BM de Waal. "Chimpanzees empathize with group mates and humans, but not with baboons or unfamiliar chimpanzees." Proc. R. Soc. B vol.281(2014) doi: 10.1098/rspb.2014.0013 (x)
Campbell, Matthew W., and Frans BM de Waal. "Ingroup-outgroup bias in contagious yawning by chimpanzees supports link to empathy." PLoS One 6.4 (2011): e18283. (x)