elephant breeding -- 7/27/15

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Today's selection -- from Elephant Don by Caitlin O'Connell. Elephants have entered the list of endangered species. Their reproductive success is made all the more precarious in that only a few bulls within a herd enter "musth" (the frenzied state of sexual arousal) in a given year, "estrus" (heat or sexual receptivity) is infrequent among elephant cows, and gestation lasts twenty-two months:

"A bull entering the hormonal state of musth was supposed to experience a kind of 'Popeye effect' that trumped established dominance patterns. ... In fact, there are reports of musth bulls having on the order of twenty times the normal amount of testosterone circulating in their blood. ... Musth manifests itself in a suite of exaggerated aggressive displays, including curling the trunk across the brow with ears waving. ...

An African elephant chases a giraffe during musth

"Musth -- a Hindi word derived from the Persian and Urdu word 'mast,' meaning intoxicated -- was first noted in the Asian elephant. In Sufi philosophy, a mast (pronounced 'must') was someone so overcome with love for God that in their ecstasy they appeared to be disoriented. The testosterone-heightened state of musth is similar to the phenomenon of rutting in antelopes, in which all adult males compete for access to females under the influence of a similar surge of testosterone that lasts throughout a discrete season. During the rutting season, roaring red deer and bugling elk, for example, aggressively fight off other males in rut and do their best to corral and defend their harems in order to mate with as many does as possible.

"The curious thing about elephants, however, is that only a few bulls go into musth at any one time throughout the year. This means that there is no discrete season when all bulls are simultaneously vying for mates. The prevailing theory is that this staggering of bulls entering musth allows lower-ranking males to gain a temporary competitive advantage over others of higher rank by becoming so acutely agitated that dominant bulls wouldn't want to contend with such a challenge, even in the presence of an estrus female who is ready to mate. This serves to spread the wealth in terms of gene pool variation, in that the dominant bull won't then be the only father in the region.

"What makes the stakes especially high for elephant bulls is the fact that estrus is so infrequent among elephant cows. Since gestation lasts twenty two months, and calves are only weaned after two years, estrus cycles are spaced at least four and as many as six years apart. Because of this unusually long interval, relatively few female elephants are ovulating in anyone season. The competition for access to cows is stiffer than in most other mammalian societies, where almost all mature females would be available to mate in any one year. To complicate matters, sexually mature bulls don't live within matriarchal family groups and elephants range widely in search of water and forage, so finding an estrus female is that much more of a challenge for a bull."