Friday, November 4, 2011

Happy Zebra clan and clues to social organization

Most of the end of October I was in Nairobi and that was long enough. By the time I returned to the Mara the migration activity had begun to subside and Happy Zebra clan was relocated in my absence. Uncovering the whereabouts of the Happy Zebra communal den seems blog worthy just given the amount of time and effort we have invested in pursuit of these animals. From call play backs, to checking old dens, to driving the most extreme edges of this clan’s suspected territory, and waiting nights after dark trying to pinpoint the location of distant whoops… we tried for the better part of September and October to find Happy Zebra. The unknown with this clan did not however begin when CSBY (the last adult female to occupy Alamo Den) was last seen with her two 4-week old cubs at the previous communal den. As earlier discussed on the blog, the death of KOI by lions removed the highest-ranking individual from the clan. This opened up Happy Zebra to uncertainty (at least for us observing) or possibly opportunity (for other females in the clan) as the social organization was determined to shift.

At the time of KOI’s death, Happy Zebra was composed of 11 adult females, 9 cubs, 6 subadults, and 4 adult males. KOI and her lineage comprised about 33% of the total Happy Zebra clan. All else equal and following the conventional inherited social rank descendent from KOI, COEL (KOI’s youngest female cub) should have been successive dominant female of Happy Zebra clan. However, given that COEL was less than a year old, this cub’s survival, far less its dominance, was not certain. The possible other successors to dominance could in theory have been any female in the clan, though most likely it would be some relation to KOI that arrived at the top. A breakdown of KOI’s lineage and prospective inheritance of dominance in Happy Zebra were organized in a list from a previous post, To discern the newest rank relations we would have to observe and record a series of dyadic interactions and tally aggressions and submissions between individuals in a matrix. The first steps…observe behavioral interactions.
On October 31st, 2011 I saw Happy Zebra present at their communal den. Most notable in this session was the confirmation of PIKE (one of KOI’s older daughters and a likely candidate for the highest rank individual in Happy Zebra) having two 4 week old cubs. Also of interest were a number of interactions, which occurred between the female members of KOI’s lineage. PIKE’s cubs were confirmed after they were seen nursing from PIKE. Also nearby was BOOM, a previous female offspring to PIKE. Like many female subadults interested in the business of babies, BOOM was being pesky and bothersome to the nursing PIKE. Not very note worthy in and of itself. However, a good context to achieve a brief, instantaneous glance at the social hierarchy is through a cascade of aggressions. For example if a high rank individual aggresses on a mid rank individual, and then the mid-rank individual takes out that aggression on low rank individual, we note the latter aggression as a scape goat context. It could be like, when my girlfriend reprimands me, and in my frustration I vent on my dog (that is assuming my dog doesn’t out rank me…data is still out on that); either way the aggression filters down through the ranks, clearly revealing who is dominant. Anyway my point, was that in being pesky to PIKE, BOOM was aggressed upon. It was also the case that COEL (KOI’s youngest cub and technically rightful heir to dominance) had recently arrived at the den.

COEL cautiously approaching one of PIKE’s newest cubs (the small black one on the right).

The good news is that the ~1 year old orphan persisted through the migration season unaided by her mother. However, after being aggressed on by PIKE, BOOM redirected that aggression to COEL, who submitted and retreated. Shortly after words PIKE and BOOM, in a coalition aggression, again displaced COEL.

PIKE and BOOM in the background before they aggress on and displace COEL, who is already beginning to go ears back (a sign of submission).

Although far from conclusive, at the surface it seems that without the support of her mother to reinforce her social standing, COEL may not befall the highest rank spot in Happy Zebra. Other clues, like COEL arriving and flattening her ears as she approached to greet PIKE and BOOM also suggests her subordination to these two. More evidence is needed, including the observation of interactions between PIKE and some of the other adult females in this clan, but this was a good start to reorganizing the Happy Zebra social hierarchy.

Michigan State University | College of Natural Science