Hyenas Eschew Lent, Chew Donkeys Instead
Anyone who has ever attended a holiday parade or gone on a summer vacation knows that cultures tend to create their own seasonal patterns. In much of Western culture, December is a time of much celebrating and feasting, while similarly wintry January is relatively dreary and dull (after New Year’s celebrations subside). This raises a question: how do the behaviors and culture of a society affect the animals that depend upon that society's garbage for their food? The progressive encroachment of human settlements into the habitats of wild animals has opened opportunities for animals to avail themselves of human refuse. A raccoon in North America is likely to find a juicy watermelon rind in July and leftover turkey remains in November. Perhaps equally enticing for a roving dumpster-diver, but by no means nutritionally equivalent.
Many holidays are based—with varying degrees of stricture, divergence, and commodification over time—on religious tenets. In turn, religion can exert a powerful influence on the dietary habits of its adherents. The foundational texts of today’s three dominant monotheistic religions—Islam, Judaism, and Christianity—are extremely detailed in describing food taboos, instructions for ritual food sacrifice, and procedures for penitential fasting. From Ramadan to Lent to the maintenance of Kosher kitchens, people across the globe design their diets based upon the dictates of their given creeds.
This brings us back to the issue of how cultural “seasons” affect the food intake of scavengers. It stands to reason that urban carnivores will be indirectly subjected to the vagaries of local humans' dietary regulations. A group of researchers led by Gidey Yirga of the Mekelle University of Ethiopia sought to test this hypothesis by examining the diets of spotted hyenas (Crocuta crocuta) that have become dependent upon local human communities for food, and reported their results in the most recent issue of the Journal of Animal Ecology (Yirga et al. 2012).
Hyenas are often belittled as mere scavengers—the carrion-swipers of the African savannah. This is not quite fair: studies have shown that hyenas kill between the vast majority of the prey that they consume (Kruuk 1972). In some areas, however, habitat destruction and the progressive spread of human settlements have depleted prey populations to the point that hyenas and other carnivores must resort to killing livestock and scavenging waste from villages in order to survive.
Many denizens of Northern Ethiopia adhere to the Ethiopian Orthodox Tewahedo Church. The church mandates seven fasting periods, the most significant being the “Abey Tsome” (Lent) period lasting for 55 days leading up to Easter. During this time, adherents must maintain a diet free of all animal products (essentially a vegan menu), and are limited to one meal per day, which must not be eaten before mid-afternoon. Concomitantly, the slaughter of animals greatly declines during the Lenten period, and the reduced amount of food that is prepared consists nearly entirely of plant products. The research group led by Yirga predicted that this would impact local hyenas by changing the composition of their diet and forcing them to otherwise supplement themselves by increasing their hunting activity. Hyenas don't do vegan very well.
It is noteworthy that although lions do actually scavenge quite a bit (Schaller 1972), they were not chosen for this study because they are not well tolerated by humans. Hyenas rarely attack humans, and face less persecution by villagers than do their feline counterparts. Because humans go to lengths to keep lions away from their living areas, they likely have less access to garbage and would not be a less ideal model than hyenas for a study on the effects of anthropogenic waste on scavenger diets.
The researchers cordoned off sample plots in areas near villages where scavenging hyenas were known to roam. They collected dung from the plots on the first day of the fast, in order to obtain a record of the hyenas’ diets prior to the fast. They then collected dung on the last day of the fast, to represent their dietary intake while their human neighbors were temporarily vegan. They then collected samples again 55 days after Easter, to determine the hyenas’ post-fasting diet.
The results upheld the hypothesis that religiously dictated changes in human diets also altered the composition of the hyenas’ diets. The scats deposited during the fasting period differed significantly from those deposited during both the pre- and post-fasting periods, and the pre- and post-fasting dietary composition did not differ significantly.
It appeared that when the availability of animal products in human refuse petered out, hyenas resorted to hunting, primarily targeting donkeys. Donkeys are common in the region, and, according to Yirga et al., are not corralled and protected as stringently as are cattle. As a result, during Abey Tsome the proportion of donkey remains in hyena scats spiked, indicating that they were hunting in order to supplement the meager vegan leftovers that were filling dump sites.
There is a caveat in the study: although donkey remains did increase significantly during Abey Tsome, the prevalence of cattle hair in the scats remained high throughout the fasting period. The authors note that the Tigray People’s Liberation Front (TPLF), an Ethiopian political group (or rebel group, depending upon your leanings in local politics; it has been accused of diverting aid money from famine victims) celebrated their 35th anniversary during the fasting period, which resulted in cattle slaughters despite the church’s dietary rules, likely supplying hyenas with more cattle remains than would normally have been available during a fasting period. Another hiccup in the study is that the number of samples from the fasting period were low because “the plots had been plowed by farmers,” although there is no indication as to how far along in the fasting sample period that disruption occurred.
Despite the two hiccups in sampling conditions, the results of this study are statistically significant and carry important implications. In fact, without the TPLF celebration, it appears likely that the results would have been even more significant, although follow-up studies will be needed to verify this. It also seems that the exclusion of lions from areas surrounding human settlements may hyena foraging habits when they are forced to hunt, and it would be interesting to see a study comparing the habits of hyenas that are sympatric with lions with those in "lion exclusion zones" around villages.
The take-home message of this study is that human food habits can indeed influence the dietary composition of urban carnivores, potentially creating much different nutritional conditions for these populations relative to their rural conspecifics. In addition, the composition of the supplemented diet can vary with religious seasons and holidays, creating a kind of anthropogenic seasonality in the “prey” availability and hunting habits of dependent carnivores. This is an important issue for both scientists and local citizens to recognize and understand. As more and more natural habitat disappears, the lifestyles of humans and local wildlife will become, for better or worse, more and more intricately entwined.
Kruuk, H. 1972. The spotted hyena. A study of predation and social behavior. The University of
Chicago Press, Chicago.
Schaller, G. B. 1972. The Serengeti Lion. The University of Chicago Press, Chicago.
Yirga, G., De Longh, H. H., Leirs, H., Gebrihiwot, K., Deckers, J., & Bauer, H. (2012). Adaptability of large carnivores to changing anthropogenic food sources: diet change of spotted hyena (Crocuta crocuta) during Christian fasting period in northern Ethiopia Journal of Animal Ecology, 1052-1055 DOI: 10.1111/j.1365-2656.2012.01977.x