Vol. 15 - Deutsches Primatenzentrum

Lemur News Vol. 15, 2010 Page 15
Observations
The event was observed during regular behavioural observations
of red-fronted lemurs in Kirindy Forest,60 km north of
Morondava. It was the only snake-lemur interaction observed
during the entire study period from November 2007
to April 2010, in which four lemur groups were followed
daily by one or two observers,respectively (> 4,000 h of observation
data).Red-fronted lemurs live in multi-male,multifemale
groups of 5-12 individuals (Pereira and Kappeler,
1997;Wimmer and Kappeler,2002).The study group (B) that
encountered the boa included 9 individually marked animals
at the time (2 adult females, 5 adult males, 1 juvenile male, 1
male infant).
On March 1,2010,at 7.19 h,sudden alarm calls of several redfronted
lemurs were heard in the study area known as CS7.
Six individuals (2 adult females,2 adult males,1 juvenile male,
1 male infant) could be identified after approaching the group
to within 10 m.Three of them (2 adult females,1 adult male)
emitted "Woofs" and "Huvvs",vocalisations typically uttered
during predator encounters (Fichtel and Kappeler, 2002).
The 5 individuals surrounded an approximately 2 m long
Madagascar ground boa (Fig. 1) that was lying motionless on
the ground. The lemurs sat at a height of 1-2 m, each about
3 m away from the snake, wagging their tails vigorously, ex-
Fig. 1: Madagascar ground boa in Kirindy. (Photo: Lennart
Pyritz)
cept the infant that kept a distance of 5 m during the entire
event and did not display any vocalisations or tail-wagging.
During the next 4 min,one of the adult males approached the
front end of the boa twice, getting as close as 1-2 m. After 5
min, he left the scene. During this time, one of the adult females
also approached the snake up to within 2 m.When the
male left,the second female started to quickly circuit the boa
for 4 min,maintaining a distance of 2-3 m.After 14 min of several
approaches and continuous alarm calls by 3-5 individuals,
the boa moved for the first time,heading slowly away.The remaining
adult male approached the moving snake also within
2 m; also at its front end. About 1 min later, the boa had
moved 15 m away, and the lemurs left in the opposite direction,still
uttering grunts continuously.Once the boa was out
of sight, the mobbing stopped and the lemurs` behaviour returned
to baseline levels.
Discussion
The mobbing reaction of the group was strong and prolonged
and included most of the group members.This is similar
to the behaviour of a black lemur (Eulemur macaco
macaco) group encountering a Madagascar boa at Ambato
Massif, where the group mobbed the snake for 15-20 min,
and some individuals approached it as close as 1 m before
finally leaving the location (Colquhoun, 1993). It is also noteworthy
that females and males mobbed and approached the
snake in equal measure as observed in a number of other
species (e.g., Tamura, 1989; Ferrari and Ferrari, 1990; Tello et
al., 2002). The infant maintained a larger distance to the boa
and did not engage in the mobbing displays, however. Similar
infant behaviour has also been reported for other primates
(e.g., Ferrari and Ferrari, 1990) and might be due to a higher
susceptibility to an attack due to smaller body size or a lack
of innate experience regarding predator encounters and
mobbing strategies (Curio et al., 1978; Fichtel, in press).
The strong mobbing reaction of the lemurs might be explained
by the hunting strategy of the snake.Boas are ambush
hunters that usually abandon an attack as soon as they have
been detected (Montgomery and Rand, 1978; Slip and Shine,
1988). Therefore, it seems beneficial for prey animals to signal
the ambush hunter quickly and distinctly that it has been
detected. As boas do not pursue their prey after an unsuccessful
attack, it is also unsurprising that the lemurs’ behaviour
returned to baseline levels of anxiety shortly after departing
the site of the predator encounter. In contrast,
groups of red-fronted lemurs showed increased vigilance behaviour
for at least 30-60 min after encountering a fossa
(Cryptoprocta ferox;pers.comm.Jean-Pierre Tolojanahary and
pers.observation by LP),which is probably due to the higher
agility and climbing abilities of the largest mammalian carnivore.Furthermore,fossas
have been observed to hunt cooperatively
and pursue prey up to 45 min (Lührs and Dammhahn,
2009).
There are no quantitative data on predation rates of lemurs
by snakes in Kirindy, only opportunistic observations (e.g.,
Schülke, 2001; Eberle and Kappeler, 2008) that are biased by
several factors, however. The low observation rate of boalemur
interactions could be due to the reptiles` nocturnal
lifestyle (Raxworthy,2003),so that most of the attacks would
occur at night when no or only few observers are working in
the forest. Furthermore, boas at Kirindy are only active during
the rainy season from January to April, when observations
are often limited by dense foliage and frequent rainfalls.
Five of the six individuals taking part in the mobbing were related
(1 adult female and her 4 offspring from the last 4
years), while it is currently unknown whether the second
adult male sired one of the two youngest group members.
However, due to the small number of detailed observations
of predator encounters it remains impossible to identify the
ultimate causes of collective mobbing (kin defence/parental
care, self-/group defence or cultural transmission of enemy
recognition; Curio et al., 1978) in this species for the time
being.
Acknowledgements
LP was supported financially by the Deutsche Forschungsgemeinschaft
(DFG; KA 1082/16-1, FuE). We thank field assistant
Jean-Pierre Tolojanahary for sharing his long-term observation
experiences with us. We are also grateful to Peter
Kappeler, Claudia Fichtel and Moritz Rahlfs for constructive
and helpful comments on earlier drafts of the manuscript.
References
Burney, D.A. 2002. Sifaka predation by a large boa. Folia Primatologica
73: 144-145.
Caro, T. 2005. Antipredator defenses in birds and mammals.
The University of Chicago Press, Chicago, London.
Colquhoun, I.C. 1993. The socioecology of Eulemur macaco:
A preliminary report. Pp. 11-23. In: P.M. Kappeler; J.U.
Ganzhorn (eds.). Lemur social systems and their ecological
basis. Plenum Press, New York and London.