Cathemerality in wild ring-tailed lemurs (Lemur catta) in the spiny forest of Tsimanampetsotsa National Park: camera trap data and preliminary behavioral observations.

Cathemerality consists of discrete periods of activity during both the day and night. Though uncommon within Primates, cathemerality is prevalent in some lemur genera, such as Eulemur, Hapalemur, and Prolemur. Several researchers have also reported nighttime activity in Lemur catta, yet these lemurs are generally considered "strictly diurnal". We used behavioral observations and camera traps to examine cathemerality of L. catta at the Tsimanampetsotsa National Park, Madagascar. Nighttime activity occurred throughout the study period (September 2010-April 2011), and correlated with warm overnight temperatures but not daytime temperatures. Animals spent 25% of their daytime active behaviors on the ground, but appeared to avoid the ground at night, with only 5% of their time on the ground. Furthermore, at night, animals spent the majority of their active time feeding (53% nighttime, 43% daytime). These findings imply that both thermoregulation and diet play a role in the adaptive significance of cathemerality. Additionally, predator avoidance may have influenced cathemerality here, in that L. catta may limit nighttime activity as a result of predation threat by forest cats (Felis sp.) or fossa (Cryptoprocta ferox). Further data are needed on cathemeral lemurs generally, but particularly in L. catta if we are to fully understand the evolutionary mechanisms of cathemerality in the Lemuridae.