Population demography and social structure changes in Eulemur fulvus rufus from 1988 to 2003

Abstract

Eulemur fulvus rufus has been described as having stable multi-male/multi-female groups, a male-biased sex ratio, and female philopatry. However, in a 16-year study of this subspecies we documented a great deal of demographic change as several groups permanently fissioned, some groups disappeared, and new groups formed. We split the dataset into two periods, 1988 to 1993 and 1994 to 2003, which coincided with the first disappearance of a study group (in August 1994) and the first permanent group fission (in December 1994). The average group size decreased by nearly half between the study periods (10.5-5.6), while the frequency of group membership changes increased (2.0-8.3 times/year), and the birth rate decreased (0.56-0.38). Females, as well as males, immigrated into study groups and transferred between groups, something that has been rarely seen in this subspecies. We also found a significant decline in the amount of fruit from the earliest part of the study to the latter part of the study. Study groups did not switch to other types of foods during periods of fruit shortage, but traveled outside of their home range areas more often over the study period. Finally, the density E. f. rufus decreased in the study area while the densities of their main food competitors, Varecia variegata and Eulemur rubriventer, increased. Although few primate populations are numerically stable over time, we suggest that female behavioral responses to decreases in fruit availability may have influenced some of the demographic changes we witnessed in this study.

Global climate cycles and cyclones: consequences for rainfall patterns and lemur reproduction in southeastern Madagascar

“…Not all lemurs in the region may be similarly affected by cyclone landfall, however. Erhart & Overdorff (2008a) found that birth rate did not differ for Eulemur fulvus rufus in Ranomafana between cyclone/ tropical storm and nonstorm years (Kendall Rank Correlation: t 5 0.24, Z 5 0.75, P 5 0.45), however, the sample size of adult females each year for that study ranged between only one and four individuals.…”

“…Negative impacts of cyclone landfall on fruit availability have also been shown in our study area. Erhart & Overdorff (2008a) documented that the percentage of large trees bearing fruit dropped strongly after cyclone landfall, with some cyclones leaving no fruit (after cyclone Alibera, Category 4) to only 1% remaining (cyclone Manao, Category 2). Our current study is the first that we are aware of to suggest, based on nonanecdotal accounts that cyclones can exert strong influence on the population dynamics of a long-lived primate species through reductions in fecundity, affecting both birth rates and first year survival.…”

Group size predicts social but not nonsocial cognition in lemurs

“…Lemur catta are characterized by a multi-male, multi-female social system and reside in the largest groups of any lemur species (mean group size: 15.6) [31]. Eulemur fulvus and Eulemur macaco have the next largest social groups in our sample, and live in multi-male, multi-female groups, which are smaller than those of Lemur catta (mean group sizes -Eulemur fulvus: 8.5; Eulemur macaco: 9.9) [32,33]. Propithecus coquereli and Varecia variegata live in groups ranging from adult pairs, to small multi-male, multi-female groups (mean group sizesPropithecus coquereli: 6.1; Varecia variegata: 5.4) [34,35].…”

Patterns of movement and seed dispersal by three lemur species

“…Since the home ranges were estimated based on our limited study period, they may underrepresent year-long range sizes because ranges may shift over seasons in relation to resource availability [Erhart & Overdorff, 2008a]. Indeed, cumulative estimates of daily homerange sizes did not reach an asymptote by the end of the sampling period.…”

“…These three lemur species were observed to emigrate from their natal groups at least once in their lifetime [Baden, 2011;Overdorff & Tecot, 2007;Overdorff et al, 1999]; therefore they may contribute to long dispersal of their food trees that are fruiting during their emigration period. Primates with more fluid social structures, such as group fissionfusion strategy observed in E. rufifrons [Erhart & Overdorff, 2008a;Overdorff et al, 1999], can also cover large ranges leading to a higher probability of seed dispersal across different microsites and a scattered seed dispersal pattern [Chapman & Russo, 2006]. The observed frequency distribution of estimated seed-dispersal distances by V. v. editorium showed a peak close to the parent tree, followed by a rapid decline and a long tail.…”