Density Of Lemur Catta And Home Range Size In Different Habitats

Biomass and home ranges of L. catta vary greatly with habitat. Berenty reserve in southern Madagascar is a 200-ha forest fragment containing four distinct and adjacent habitats: riverine (gallery) forest, second-growth deciduous forest with 15-20 m of canopy, xerophytic scrub forest, and spiny forest (Budnitz and Dainis, 1975; Jolly, 1966; Jolly et al., 2002, 2006). L. catta densities vary markedly between habitats from 250 to 500 lemurs/km2 in gallery and second growth

Figure 2. (Cont'd.) Photos of lemur catta in 3 different habitats: (a) ring-tailed lemurs in a tamarind tree in gallery forest at the Beza Mahafaly Special Reserve. The ring-tailed lemurs here are collared and tagged as part of a demographic and health study (photo by L. Gould), (b) on a rocky outcrop at Anja private reserve (photo by M. L. Sauther); and (c) in the far south near Cap Ste. Marie in Opuntia cactus hedges (photo by E. A. Kelley).

Figure 2. (Cont'd.) Photos of lemur catta in 3 different habitats: (a) ring-tailed lemurs in a tamarind tree in gallery forest at the Beza Mahafaly Special Reserve. The ring-tailed lemurs here are collared and tagged as part of a demographic and health study (photo by L. Gould), (b) on a rocky outcrop at Anja private reserve (photo by M. L. Sauther); and (c) in the far south near Cap Ste. Marie in Opuntia cactus hedges (photo by E. A. Kelley).

forest to 100/km2 in scrub and spiny forest fragments (Jolly et al., 2006). Mean group size at Berenty is also dependent upon habitat with the smallest groups (mean =8.9 individuals) in the spiny forest, while larger groups average 11.8 animals in gallery forest and 13.9 in the tourist area (Jolly et al., 2002; Koyama et al., 2002). Pride (2005) suggests that L. catta at Berenty may live at the highest density of all populations. Pride found that short-term food scarcity in the dry season affected larger groups more seriously in terms of physiological stress (higher cortisol concentrations), as resource competition in a large group was higher than in groups with fewer individuals. Pride suggests that living in intermediate-sized groups may be optimal, particularly for females, in terms of resource competition and availability. Within-group sex ratio at Berenty varies from 9 adult males and 3 adult females to 1 male and 5 females (Jolly et al., 2002). In gallery forest areas, home ranges vary from 3.95 to 16.7 ha, and in the less dense xerophytic/scrub forest, home ranges of 12-25 ha are reported (Jolly et al., 1993).

Beza Mahafaly Special Reserve in southwestern Madagacar consists of two parcels: parcel one is an 80-ha area of undisturbed gallery and xerophytic forest, and parcel two consists of 500 ha of xerophytic and spiny forest. Demographic data were collected between 1987 and 2001 on the ring-tailed lemur population in parcel one (Gould et al., 1999, 2003; Sussman, 1991). The average density of adult animals in this parcel of forest is 87.5 adults/km2 and 137.5/km2 when subadults are included (Gould et al., 2003), and actual density ranges from 90 to 135

animals/km2 depending upon microhabitat (Sussman, 1991). In nondrought years, the Beza population stabilizes at 60-70 adults and 100-110 animals including immatures (Gould et al., 2003), although this is in the reserve itself: groups of L. catta live outside the reserve as well, so there is a continuous population in the forested areas of this region. Home ranges vary from an average of 17 ha in the eastern gallery forest area to 32 ha in the drier vegetation-sparse western part of the reserve (Sussman, 1991). Average group size at Beza is 11.5 animals and sex ratio is 0.92. Whitelaw and Sauther (2003) found that lemur density in the degraded gallery forest 1 km north and south of the reserve was just half of that inside the protected area. The population in the reserve forest itself may reflect optimum carrying capacity in that habitat (Gould et al., 2003).

At two other sites, population density varies markedly from that reported at Berenty and Beza Mahafaly. At Andohahela National Park in the extreme south, L. catta density ranges from 8 to 64 animals/km2 with fewer lemurs found in the disturbed dry forest habitat than in nondisturbed gallery forest (Raharivololona and Ranaivosoa, 2000). Ring-tailed lemurs inhabiting the mountainous Andringitra region live at a very low density of 22.8 individuals/km2 (Rakotoarisoa, 2000). One group studied by Rakotoarisoa lived in an area more than 2000 m in elevation while the other group was found at a lower elevation. The home ranges of these high-altitude L. catta occur vertically: the two groups studied by Rakotoarisoa used vertical areas from 1310 to 2360 m and 1250 to 2040 m. They use fissures or overhangs as sleeping sites, which Goodman et al. (2006) suggest may protect them from the fossa (Cryptoprocta ferox), a viverrid predator that is present at Andringitra. Day range is large for these lemurs: they cover more than 100 ha daily (1000 m), much of this vertically. Average day range for ring-tailed lemurs at Berenty and Ansirananomby, topographically flat areas, is 1377 and 950 m, respectively (Jolly et al., 1993; Sussman, 1972, 1999).

Jolly and Pride (1999) and Mertl-Milhollen (2000) found that home range sizes in the gallery forest at Berenty have remained stable since first studied in either the early 1960s or early 1970s. At Beza Mahafaly, while some groups dissolved during a 15-year demographic study, others persisted, and home ranges were also stable (Gould et al., 2003; personal observation). Jolly and Pride (1999) suggest that benefits of such stability and detailed knowledge of resources in the range may extend beyond a given season, representing a benefit for future generations. During flowering or fruiting periods, groups at both sites have been observed leaving the home range core to exploit these rare resources (Jolly and Pride, 1999; Sauther, 2002; Sussman, 1991).

SOCIAL ORGANIZATION, GROUP STABILITY, AND GROUP FISSION

Ring-tailed lemur groups consist of a core of adult females and offspring, one or a few central males, and peripheral males, which disperse at sexual maturity and sometimes migrate several times during their lives (Gould, 1997; Jolly, 1966; Sauther,

1992; Sauther et al., 1999; Sussman, 1992). Larger groups sometimes contain more than one matriline, and in such a case, one will be dominant to the other(s) (Nakamichi and Koyama, 1997; Sauther, 1992; Taylor and Sussman, 1985).

In both wild and free-ranging captive populations, when groups become too large, eviction of subordinate females and group fission often occur (Gould et al., 2003; Jolly et al., 2002; Koyama, 1991; Koyama et al., 2002; Sussman, 1991; Taylor and Sussman, 1985). Targetted aggression by dominant females towards subordinate ones usually results in group fission. Such aggression has been documented at both Berenty and Beza Mahafaly Reserves, as well as in free-ranging captive situations (Gould et al., 2003; Jolly et al., 2002; Koyama et al., 2002; Pereira and Kappeler, 1997; Sauther et al., 1999; Takahata et al., 2005; Vick and Pereira, 1989). Jolly et al. (2002) suggest that such evictions may occur because it may be less costly for dominant females to evict their female cousins than to expand their home ranges, since range expansion could result in costs such as increased travel time and resource competition and physical confrontation with other groups.

Group fission at Berenty occurs when group size reaches 15-25 individuals (Jolly et al., 2002). A new group establishes a small home range between the group that expelled them and their competitive neighbors. Costs to a new group arising from fission include increased aggression from neighboring groups and increased infant mortality. At Beza Mahafaly, few groups reach 20 animals, but group fissions have been documented in four of the groups living in the reserve over an 18-year period (Gould et al., 2003; Sauther, personal communication; Sussman, 1991). Home ranges of fissioned groups at Beza are either identical to that of the parent group or part of the parent group's home range is incorporated in the new home range (Gould et al., 2003; Sussman, 1991). Dissolution has also been observed at Beza Mahafaly when groups have become very small, e.g., 2 to 3 individuals (Gould et al., 2003).

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