pdfs.semanticscholar.org/8b15/89dcb59b230c2b1726424a065ecab6e7ca3d.pdf As western lowland gorilla groups are predominantly single male (Section 1.4), western lowland
silverback protective functions may be even more vital than for mountain gorilla silverbacks,
who can often rely on the support of other adult male members in their group. Additionally aside
from the obvious risk of infanticide, much of western lowland habitat is fraught with risks (ie.
poaching, elephants, leopards) that have greatly decreased or altogether disappeared in
mountain gorilla habitat (Section 1.3; Chapter 3).
While leopards have all but disappeared from montane mountain gorilla habitats [Sholley,
1991], they are still the apex predator (excluding humans) for larger mammals within the
rainforests of Central and Western Africa [Henschel, 2008; Jenny & Zuberbuhler, 2005].
Leopards in rainforest environments preferentially hunt medium sized species (7-30 kg) [Hart et
al., 1996; Henschel et al., 2005; Ososky, 1998; Ray & Sunquist, 2001] although depletion of
preferred prey items through unsustainable bushmeat practices force cats to hunt outside of
their favoured weight range [Fay et al., 1995; Henschel, 2008; Nowell & Jackson, 1996].
Evidence from previous studies suggests that forest leopards may adapt their hunting
behaviour to follow individual preferences for particular prey species [Jenny & Zuberbuhler,
2005; Zuberbuhler & Jenny, 2002].
Although the actual level of risk faced by western lowland gorillas as a result of leopard
predation is uncertain, evidence is mounting to suggest that they along with other apes are
targeted as leopard prey. In the early 1960s, Schaller [1963] confirmed the deaths of 2-3 adult
male mountain gorillas due to leopard attack. During a five year period in Taï National Park,
Côte d’Ivoire, Boesch [1991] documented nine separate leopard attacks on chimpanzees.
Leopard predation was also strongly suspected in the death of a silverback at Mbeli Bai,
Republic of Congo, and of a blackback at the Lossi study site, Democratic Republic of Congo
[Robbins et al., 2004]. Fay et al., [1995] and Watson [1999] witnessed leopard attacks on adult
gorillas at both gorilla habituation study sites (Bai Hokou/Mongambe) in the Dzanga-Sangha
Protected Areas Complex, Central African Republic. Furthermore in 1999, the Bai Hokou study
group’s main silverback was severely injured in an attack which led to his eventual demise.
Although the attacking species could not be verified, attempted leopard predation was
suspected due to suspicious claw-like markings on the focal adult male’s back [Cipolletta, 2003;
Cipolletta pers. comm.]. Additional records at Bai Hokou show that leopards were detected near
gorilla groups on three occasions and that their presence affected group ranging patterns
[Goldsmith, 1999; Klailova pers. obsv.]. Finally, although scavenging cannot be ruled out, gorilla
and chimpanzee remains in leopard faeces have been recorded at various rainforest sites [Fay
et al., 1995; Hart et al., 1996; Henschel et al., 2005, 2008; Ososky, 1998; Tutin & Benirschke,
1991].
The slow life histories of gorillas coupled with a growing inventory of suspected and verified
predation incidents, suggest that the leopard could be an important cause of mortality in some
ape populations [Robbins et al., 2004]. However, due to the cryptic nature of the forest leopard
and challenges of western lowland gorilla habituation, it has not been possible to systematically
assess leopard predation risks to gorilla groups.
More examples of the silverback’s protective role and the delicate interplay between infanticide,
predation, and disturbance related risks (i.e. elephants) will be detailed in the forthcoming
chapters.
Understanding the western lowland silverback’s role in relation to his females’ reproductive
success and therefore his own reproductive success requires an initial assessment of his role,
detailing when and how it operates. This appreciation of his role will further enable
understanding of how variations in silverback functions underlie infant survival and female
reproductive performance