Diet And Feeding Ecology

The ring-tailed lemur has been classified as a frugivore/folivore and an "opportunistic omnivore" (Sauther, 1998; Sauther et al., 1999; Simmen et al., 2006a) and is able to adapt to marked shifts in diet following the wet and dry seasons. In fact, the feeding ecology of L. catta is finely tuned to the seasonality of their food resources and certain key species are relied upon during different phases of the reproductive cycle (Sauther, 1998). Probably the most important food resource for forest-dwelling L. catta is the tamarind tree (Tamarindus indica), known in Madagascar as "kily." The importance of kily to ring-tailed lemurs will be discussed later in the chapter.

Resource availability is strongly tied to reproduction in this species (Rasamimanana and Rafidinarivo, 1993; Sauther, 1992, 1993, 1998;Yamashita, 2002). Although food resource availability is low during gestation, availability of plant foods increases dramatically with the onset of the rainy season, which corresponds with the period of female lactation and infant weaning. More fruit available at this time means higher energy for lactating females and high-quality foods for weanlings (Jolly, 1984; Sauther, 1992, 1998).

Simmen et al. (2006b) present an exhaustive summary of all plants eaten by L. catta at the Berenty, Beza Mahafaly, and Antserananomby sites. Feeding ecology has been studied over annual cycles at both Berenty and Beza Mahafaly; L. catta use 82 plant species for leaves, 40 for fruits, and 16 for flowers at Berenty and 40 species for leaves, 28 for fruit, and 16 for flowers at Beza Mahafaly. They use resources as they become available, and key foods (other than tamarind) can change from one month to the next. At both sites, two or three plant species comprise the major part of the diet each month and animals shift to different plants species when they become available (Sauther, 1992, 1998; Simmen et al., 2006b).

Ring-tailed lemurs can handle both ripe and unripe fruit, young and mature leaves, leaf stems, flowers, and unripe seeds, and they regularly ingest dead wood, termite soil, and earth (Rasamimanana and Rafidinarivo , 1993; Sauther, 1992, 1998; Simmen et al., 2003, 2006b; Sussman, 1972). As in other primate species, geophagy in ring-tailed lemurs is likely a strategy to handle and neutralize toxic secondary compounds such as tannins (Krishnamani and Mahaney, 2000; Simmen et al., 2006a,b). L. catta do take some animal prey, consuming larvae, locusts, cicadas, spiders, spiderwebs (Sauther, 1992), and occasionally even birds and chameleons (Oda, 1996; Sauther, 1992).

Fruit abundance has been cited as the primary limiting factor in L. catta survival (Jolly et al., 2002), but Sauther (1992, 1998), Rasamimanana and Rafidinarivo (1993), and Mertl-Millhollen et al. (2003, 2006) also point out the importance of leaves in such a seasonally variable diet. The importance of herbaceous terrestrial vegetation for groups living in gallery and deciduous forests is noteworthy: at Beza Mahafaly, Sauther (1998) found that 54% of leaf food occurs at or near the ground.

To deal with seasonal food shortages, ring-tailed lemurs decrease their metabolism (Pereira et al., 1999) and travel outside of their home range to find food and water (Jolly and Pride, 1999; Mertl-Milhollen et al., 2006; Sauther, 1998).

Reproduction is closely tied to fluctuating seasonal resource availability in the geographic range of L. catta, and both Rasamimanana and Rafidinarivo (1993) and Sauther (1994, 1998) found specific feeding patterns among reproductive females at Beza Mahafaly and Berenty reserves, respectively. During gestation season at Beza Mahafaly, pregnant females fed more on flowers and fruit (excluding tamarind) while males consumed more leaves (Sauther, 1994, 1998). Lactating females focused on easily digestible young leaves, avoiding mature leaves that are high in secondary compounds. Sauther points out that immature leaves contain higher amounts of calcium, protein, and energy, crucial nutrients for nursing mothers. She found that males focused on more fruit and resorted to consuming mature leaves when alternative resources were scarce. In contrast, in gallery forest at Berenty, Rasamimanana and Rafidinarivo (1993) found that pregnant females concentrated mainly on mature tamarind leaves and unripe tamarind fruit, but became more frugivorous during the birth and lactation period. They note that while tamarind fruit is high in tannins, it is also high in protein.

Concentrations of secondary compounds in L. catta's plant foods also correspond with the marked seasonality in this region of Madagascar. Simmen et al. (2006a) found strong seasonal differences in the proportions of protein, pheno-lics, and tannins in the diet of L. catta at Berenty, which reflected differences between the dry season diet composed mainly of leaves and unripe fruit, and the largely ripe fruit diet during the wet season. Tannin content is high in many ring-tailed lemurs foods, but Ganzhorn (1989) and Simmen et al. (2006a) suggest that tannin tolerance is also high. To offset the effects of these secondary compounds, geophagy has been observed at both Berenty and Beza Mahafaly sites.

Goodman et al. (2006) found that the diet of L. catta inhabiting the Andringitra high-altitude region is markedly different from that of gallery or dry forest groups. A comparison of plants eaten by L. catta at Andringitra and Beza Mahafaly revealed that not one species was shared. The diet of this high-altitude population is comprised of 75% fruit, 8-12% leaves, and 6-12% twigs, stems, and insects (Goodman et al., 2006).

Introduced plants are important resources for the gallery forest L. catta at Berenty (Crawford et al., 2006; Soma, 1994). Soma found that when the availability of indigenous plant foods was low, both fruit and flowers of introduced species were abundant, and he suggests that these immigrant plant foods lessen the effect of extreme food seasonality in this part of the reserve. Leucaena leucocephala, another introduced tree in this forest, is consumed by gallery forest groups, and has had seriously negative consequences (Crawford et al., 2006). Since the late 1990s, ~25% of the individuals living in gallery forest at Berenty experience extreme seasonal fur and weight loss, which Crawford et al. associate with ingestion of leaves, flowers, and pods of Leucaena. This plant contains mimosine, an amino acid that inhibits DNA replication and protein synthesis. Leucaena is not found in the scrub/spiny forest habitat at Berenty, and no individuals residing in those areas exhibit the alopecia and weight loss conditions seen in the gallery groups. Leucaena consumption peaks during gestation period, and Crawford et al. and Jolly (in preparation) found that ingestion of this plant negatively affects infant survival. In 2004 and 2005 birth seasons, respectively, significantly more females residing in non-Leucaena areas had infants, compared with females living in areas where the plant was consumed. Jolly (2006b) notes that it is not simply a matter of infants being unable to cling to mothers suffering from hair loss, but rather the ingestion of Leucaena itself is the problem, as she found that even females with good or merely poor fur condition also lost infants in the Leucaena areas.

The Importance of the Tamarind, or Kily Tree, in Lemur catta Diet

All researchers who have examined L. catta feeding ecology in and around gallery forests emphasize the great importance of Tamarindus indica (or kily) in the diet of animals found in this habitat. Because tamarind trees produce fruit and flowers asynchronously (Sauther, 1998), this is the only food resource used throughout the entire annual cycle (Simmen et al., 2006b). At Berenty, ripe tamarind pods are relied upon during the late dry and early wet season (birth and lactation periods), and during the dry season, unripe pods and leaves form the staple diet, although many other plants are exploited for much more seasonal fruits, leaves, and flowers (Blumenfeld-Jones et al., 2006; Koyama et al., 2006; Mertl-Milhollen et al., 2003; Rasamimanana and Rafidinarivo, 1993; Simmen et al., 2003, 2006a,b). At Beza Mahafaly, L. catta groups also rely heavily on tamarind, but in addition, they consume large quantities of Enterospermum pruinosum fruit in the dry season, and Salvadora augustifolia during the birth and early lactation season (Sauther, 1998). Yamashita (2002) examining seven groups across microhabitats at Beza (gallery and drier deciduous forest) found a marked preference for tamarind fruit in all microhabitats. She suggests that since tamarind fruit is such a dominant food for all L. catta in the reserve, all other foods must be considered secondary. At both sites, when tamarind trees failed as a result of drought, ring-tailed lemur populations decreased dramatically for up to 4 years afterwards (Gould et al., 1999, 2003, Jolly et al., 2002). In 2005, two cyclones hit the Beza Mahafaly region, and tamarind fruiting failures occurred (Sauther, personal communication). Future censuses will reveal how and to what extent the ring-tailed lemur population in the reserve was affected.

In gallery forests, between 35 and 60% of total feeding time is spent on tamarind fruit and leaves (Koyama et al., 2006; Mertl-Milhollen et al., 2003). Mertl-Milhollen et al. (2003, 2006) found that leaves from closed canopy tamarinds closer to the river at Berenty contained more water and protein than did tamarind leaves in the open forest farther from a water source. They also note that water content of new tamarind leaves is more dependent on rain than the water table; but water content of mature leaves correlates strongly with proximity to the river.

Tamarind fruit consumption begins at a very early age. Simmen et al. (2006a) found that infants less than 2 months old are able to lick and feed somewhat on the sour pods, and that mother-infant interactions can be seen as an important step in the ingestion of this keystone resource.

Simmen et al. (2006b) and Sauther (unpublished data) note the L. catta play a key role in seed dispersal and germination of kily. Simmen et al. (2006b) found that seed germination is more successful and occurs far more rapidly after passing through the ring-tailed lemur's digestive tract.

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