Wednesday, December 17, 2014

Like your puppy at home?

(A blog post from Lily Johnson-Ulrich)

I’ve been back in the US for over six months now and I miss the field like crazy. Though work here in Michigan is fun, it isn’t the same as waking up to little hyena cubs romping around every day. I’ve been spending a lot of time going through my photos of the cubs and I remember how strikingly similar hyenas can be to dogs (or at least the cubs are to pups). I don’t have my own dog but I have quite a few doggy nieces and they certainly remind me of hyenas sometimes too-especially when they’re chowing down on a piece bone and carrying bones around like little trophies. Hyena cubs play just like puppies do, they love chasing sticks and playing tug of war with sticks and they love climbing on and chewing on anything they can get their teeth into (including the land cruisers as most of you have heard about).

One of our graduate students' dog, with a squirrel kill

Photo: Lily J-U
FYRE, BARI, RANG playing. Photo: Lily J-U

This similarity isn’t superficial and isn’t just us humans projecting dog-like qualities on our research subjects or hyena-like qualities onto our pets, but dogs and hyenas aren’t actually very closely related. Hyenas are in the Feliformia half of the carnivore family and are more closely related to cats than dogs (dogs are in Caniformia). Dogs and spotted hyenas do exhibit many similar traits, which in evolutionary biology, is called convergent evolution. Convergent evolution happens when two completely unrelated species independently evolve similar traits presumably as a response to facing similar environmental pressures. 

Hyenas and dogs have both evolved skulls and jaws specialized for crushing bones. In addition, hyenas and wolves have similar hunting styles, as endurance hunters. Though not incredibly fast at a sprint, they can easily run their prey to exhaustion in order to bring them down. This hunting style is also called cursorial hunting

When dogs became domesticated however, they seemed to lose their hunting ability, or perhaps hunting large prey was no longer necessary. For many years the general assumption was that humans purposely domesticated dogs from wolf pups in order to use them as hunting partners. Recently a different hypothesis for the domestication of dogs has come to some prominence. This is the self-domestication hypothesis which was put forth by Brian Hare (2012). It claims that dogs self-domesticated from wolves because being less aggressive towards humans was an advantage by allowing dogs to take advantage of a novel food source: human trash. 

The bone-crunching ability of dogs was probably a useful adaptation for surviving on human trash and leftovers and hyenas seem to be following the same path. In the city of Harar, Ethiopia hyenas feed on trash inside and outside the walls of the city. In Harar they are believed to eat bad spirits and are not just accepted but actually fed meat every night by two families.  
Man feeding hyenas trash. Harar, Ethiopia
In the hyena lab a lot of the graduate students, including me, are really interested in the effect of human disturbance on wild spotted hyenas. In the Maasai Mara National Reserve one clan that we study, the Talek clan, is the largest hyena clan on record. Their territory overlaps that of a growing Maasai town and many clan members certainly seem to be taking advantage of the human trash in the area.

Since dogs and hyenas already exhibit convergent evolution, I think hyenas could provide a modern model of the pressures that dogs faced as they were self-domesticating and possibly provide some new insights into just how the self-domestication process may have happened. Domestication takes a long time to happen naturally however and there isn’t evidence to suggest that hyenas will ever become domesticated. However, spotted hyenas are the most abundant and successful large carnivore in Africa and part of the reason for this fact seems to be their ability to cope with human-disturbance.

1 comment:

Unknown said...

wow, the self-domestication theory is wild! I've never heard that before. Who suggested that? and where can I read them? o3o

Michigan State University | College of Natural Science