The Women's Health Initiative Memory Study (WHIMS) has been much criticized and it has been suggested that subgroups of women exist for whom hormone therapy (HT) might improve or impair cognitive function. Possible modifying variables could be age, smoking, body mass index, and menopausal symptoms.
Spider monkeys are distributed widely throughout Central and South America and studies have been conducted at a variety of sites across the geographic range of the genus (see Table 1.1 in Campbell, this volume). However, detailed information about group composition and demography of spider monkeys remains largely unavailable. Because their fission–fusion social organization allows researchers to observe only a part of a group at any time, short-term surveys can rarely document overall group size and composition. Only a cumulative data set of party composition based on individual identification and longitudinal research can help determine the full composition of a group. Furthermore, the rarity of births and deaths make other demographic variables such as interbirth intervals only available through long-term investigation. In the 1980s, relevant demographic information from wild populations was available only for seven groups from five sites for three Ateles species. In this chapter, we present an updated summary of existing data on four Ateles species from 18 groups and 13 sites. We analyze both previously published and new data from these sites and compare them in order to re-examine the demographic characteristics of spider monkey groups.
Demographic data from 18 groups and 13 sites (Table 12.1) were gathered from the literature and augmented with data from a questionnaire sent to spider monkey researchers in 2005.
The main influence on primate ranging behavior is food abundance and distribution (Clutton-Brock, 1977; Bennett, 1986). Temporal variations in the availability and distribution of preferred resources shape primates' ranging patterns (Zhang and Wang, 1995; Agetsuma and Noma, 1995; Defler, 1996; Olupot et al., 1997), and can affect the size and shape of home ranges (Harvey and Clutton-Brock, 1981). Other factors known to affect primate ranging behavior include the position of water resources (Altmann and Altmann, 1970), location of sleeping sites (Rasmussen, 1979; Chapman et al., 1989), climatic extremes (Chivers, 1974), the need to patrol boundary areas of the home range (Goodall, 1986; Watts and Mitani, 2001; Williams et al., 2002), and variation in the perceived predation risk of differing habitats (Cowlishaw, 1997).
As large ripe fruit specialists, spider monkeys (Ateles spp.) are known for their relatively wide ranging behavior (van Roosmalen and Klein, 1988; Symington, 1988; Chapman, 1990; Castellanos, 1995; Nunes, 1995; Shimooka, 2005; Wallace, 2006), with only Lagothrix, Cacajao, Chiropotes, Brachyteles and possibly Oreonax displaying comparable or larger ranges within the New World monkeys. Published accounts of Ateles home range sizes vary between 95 and 390 hectares in continuous forests (Table 5.1), and the Barro Colorado Island group ranges more than 900 hectares (Campbell, 2000). As such several distinct habitat types are found in most spider monkey territories (Table 5.1).
Spider monkeys (Ateles spp.) occur from southeastern Mexico to the southern Amazonia rain forests of central Bolivia and western Brazil (Kellogg and Goldman, 1944; Hall, 1981; Collins and Dubach, 2000a; Wilson and Reeder, 2005). As with many species from tropical forests, their range has been decreasing as these ecosystems are transformed. This is very clear if we compare the distributions published by Kellogg and Goldman (1944) and by Collins and Dubach (2000a). A decrease in the distribution range of all species of Ateles during this period suggests that the numbers of all the taxa are declining. However, there are important differences among the taxa in their current distribution range, as well as in the magnitude and causes of the decline in population size.
When reviewing the conservation status of spider monkeys across their current range, the taxonomy of the group must be considered. In this volume, the Collins and Dubach (2000b) taxonomy has been adopted, which recognizes three distinct species of spider monkeys: Ateles paniscus, A. belzebuth, and A. geoffroyi (with a possible fourth species A. hybridus – see also Collins, this volume). Other authors (Groves, 1989; Iracilda da Cunha Sampaio et al., 1993; Rylands et al., 2001) have recognized as many as six distinct species with A. chamek, A. hybridus and A. marginatus all upgraded from belzebuth subspecies status. As a conservative approach and for the purposes of conservation planning, we prefer to analyze at the subspecies level thereby recognizing all 16 distinct taxa (Table 13.1).
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