Competing for milk can be a stressful thing for hyena twin siblings

May 01, 2013
Competing for milk can be a stressful thing for hyena twin siblings. Credit: IZW

Researchers from the German Leibniz Institute of Zoo and Wildlife Research (IZW) demonstrate for the first time in a free-ranging mammal that hunger and conflict for access to resources can be "stressful" for subordinate siblings and socially challenged dominant siblings, and hence increase their cost of maintaining homeostasis. These findings were published in the science journal Biology Letters.

The researchers measured the concentration of of the 'stress' hormone cortisol in the faeces of young sibling and singleton spotted (Crocuta crocuta) in the Serengeti National Park, Tanzania, which depended on their mothers for milk. "It was not known whether sibling conflict over access to milk increased concentrations of cortisol metabolites in twin littermates – we were now able to demonstrate that it significantly does", states Dr Sarah Benhaiem from the IZW, lead author of the study. Surprisingly, hunger had little effect on the cortisol metabolite concentration of singletons, whether male or female. The picture was different for twin siblings – both littermates had an elevated level when hungry. Interestingly, an even more important factor than hunger was the rivalry between twin littermates. In general, the less assertive (subordinate) cubs had higher cortisol metabolite levels than the more assertive (dominant) cubs. More interestingly still, when hungry, subordinates competing against a sister were more assertive than subordinates competing against a brother. As a result, in such situations dominant sisters had higher cortisol than dominant brothers.

For the first time in a free-ranging wild , the study shows how rivalry between twin siblings affects the cost of maintaining internal stability.

Explore further: Flu at the zoo and other disasters: Experts help animal exhibitors prepare for the worst

More information: Benhaiem S, Hofer H, Dehnhard M, Helms J, East ML (2013): Sibling competition and hunger increase allostatic load in spotted hyaenas. Biology Letters. doi: 10.1098/rsbl.2013.0040

add to favorites email to friend print save as pdf

Related Stories

Are elder siblings helpers or competitors?

Nov 22, 2012

Having elder siblings decreases mortality risk in childhood, but same-sex elder siblings are associated with lower marriage rates and fewer children for their younger siblings in adulthood, according to the ...

Recommended for you

Secret wing colours attract female fruit flies

Oct 22, 2014

Bright colours appear on a fruit fly's transparent wings against a dark background as a result of light refraction. Researchers from Lund University in Sweden have now demonstrated that females choose a mate ...

User comments : 0