Effect of social system on allosuckling and adoption in zebras

Although nursing non‐filial offspring (allonursing) represents costly behaviour to the female, it occurs in a variety of taxa, including ungulates. The only three currently existing species of zebra differ in their ecology and social system. In the wild, mountain zebra E quus zebra and G revy's zebra E quus grevyi live in arid environments, while plains zebra E quus quagga inhabit savannahs. Mountain and plains zebra mares form long‐term stable herds associated with a social hierarchy, whereas G revy's zebra mares form loose associations of short duration. In this study, we investigated the occurrence of allosuckling in three zebra species at the D vůr K rálové Z oo, C zech R epublic, during 1626 h of observation. We recorded no successful allosuckling bouts and only 1 and 22 attempts to allosuckle by foals of mountain and plains zebra, respectively, whereas we observed 117 attempts and 13 successful allosuckling bouts by G revy's zebra foals. Moreover, more than half of all observed G revy's zebra foals succeeded in allosuckling at least once. When rejecting an allosuckling attempt, G revy's zebra mares were less aggressive than mountain and plains zebra mares. When a G revy's zebra mare allowed occasional allosuckling by a non‐filial foal, the probability of long‐term allosuckling was smaller than that in mountain and plains zebra. We also present the first evidence of adoption in G revy's zebra. We suggest that higher tolerance towards non‐filial offspring, including the occurrence of allosuckling in Grevy's zebra, was affected by the different social systems of zebra species.