Vol. 15 - Deutsches Primatenzentrum

Lemur News Vol. 15, 2010 Page 19
diet of C.medius consists mainly of fruits and varying proportions
of arthropods depending on the season (Fietz and
Ganzhorn, 1999). C. medius is unique among primates because
it spends seven months hibernating during the cooler
dry-season of the southern winter (April to October),when
food and water availability are low (Petter,1978;Hladik et al.,
1980; Dausmann et al., 2004). When resting during the day
and when hibernating,the dwarf lemurs occupy tree hollows
either alone or with members of the family group (Dausmann
et al., 2005). In the wild, female C. medius usually give
birth to twins and in most cases reproduction only takes
place every second year (Fietz and Dausmann, 2006). C.
medius only reproduce after delayed emigration from their
family and successful occupation of their own territory (thus
in their third year at the earliest;Fietz et al.,2000).In addition,
their life span is restricted by their size and is usually
between 4 and 11 years for territory holders, and so opportunities
to reproduce are limited (for most animals between
one and three). Therefore, every young is a costly and valuable
investment. Avoiding predation of their young should
therefore be a critical part of parental care.
Predators of C. medius include raptors (Madagascar harrier
hawk Polyboroides radiatus, Madagascar buzzard Buteo brachypterus,
Madagascar long-eared owl Asio madagascariensis),
mammals (Fossa Cryptoprocta ferox, Narrow-striped mongooses
Mungodictis decemlineata), and snakes (Madagascar
Ground Boa Acrantophis madagascariensis, Madagascar Tree
Boa Sanzinia madagascariensis, Malagasy Cat-eyed Snake Madagascarophis
colubrinus) (Dausmann,submitted). The choice
of an appropriately sized tree hollow in which to give birth
can reduce attacks from many of these predators with the
exception of snakes which are able to enter any hollow that
can be used by C. medius.
C. medius leave their tree hollows at sunset to forage alone
but both sexes defend their shared territory. After the birth
of their offspring, both parents take turns in guarding the
young in the tree hollow throughout the night, while the
other one forages.As the young get older, the proportion of
time that parents spend guarding them gradually declines
(Fietz and Dausmann, 2003). At the age of about two weeks,
both parents leave the hollow and return only occasionally.
During this time, the young are particularly vulnerable to
predation,since they are unguarded.Later,the young accompany
the parents during their nightly excursions.
In this note, I want to describe evidence that adult C. medius
can repel larger predators and therefore guarding or at least
remaining within hearing range of the tree hollow is an effective
measure against predation of their offspring. I report an
observation in which a snake (Madagascarophis colubrinus)
tried to attack two C. medius young within a tree hollow but
was successfully repelled by the mother.
Our observation occurred in the Kirindy C.F.P.F.forest,a dry
deciduous forest near the west coast of Madagascar (60 km
north east of Morondava) during a focal animal survey of a
female C. medius on January 31st. For a more detailed description
of the area see Ganzhorn and Sorg (1996).
The female was a mother of two young aged two weeks.The
male of the pair was also being observed.The female left the
tree hollow after sunset at 18:57 hours and the male
followed at 19:01 hours.The two young were left alone in the
hollow within a dead tree (Malagasy name: Mapingo). The
entrance of the hollow was 3 m above ground. The female
started her regular patrol of the territory border, but suddenly
abandoned the patrol at 19:29 hours when about 80 m
from the hollow. She returned quickly to the hollow in
almost a straight line.On approach to the hollow,it was clear
that the two young who had been left alone within the
hollow were making loud and constant distress calls. On a
branch of the same tree at a height of about 1.5 m above
ground was a large M. colubrinus (> 1 m length) eying the
hollow. Even though this crepuscular or nocturnal snake is
mainly terrestrial, scansorial behaviour is possible. The female
approached the snake to within a few centimetres and
actively attacked it, and the snake responded by striking
towards the female.Both the adult female and the juvenile C.
medius were loudly vocalizing constantly.After three min,the
female seized the tail of the snake with both hands and bit it
about 10 cm from the end. The snake tried to drop to the
ground, but remained dangling in the female’s teeth. After
10 s of wriggling and repeated attempts to strike the female
the snake fell to the ground and moved away quickly. The
female descended to about 1 m, observed the ground for a
few minutes and then spent 15 min agitatedly observing the
surroundings at a height of about 3 m and inspecting the tree
hollow containing the young,who were still loudly vocalizing.
For the next 3.5 hours the female was moving rapidly around
within the territory, which is very unusual for a C. medius,
frequently returning and checking the tree hollow with the
young.She finally carried leaves into a new tree hollow about
50 m away and separately carried both young to the new tree
hollow. She did not return to sleep in the original tree hole
for the next two months, even though it had been used
frequently prior to this encounter.It seems puzzling that the
male of the pair did not come to help during the attack.Since
the male was followed simultaneously we know that at the
time of the attack he was less than 20 m from the tree hollow,
and clearly within hearing range of the distress calls. He
returned about 30 min after the attack where he met the
female and groomed her while she and the young continued
making distress calls. Since reproduction in this species is a
fairly rare event even including extra pair copulations, the
possibility of siring offspring is restricted, and the male
should have been highly motivated to defend his young in
order to increase his fitness. Considering the high (obligate)
paternal investment in guarding the young and the life-long
pair bond, C.medius have a surprisingly high rate (ca 40 %) of
extra pair young (Fietz et al.,2000;Schwensow et al.,2007).It
is thought that the male cannot discriminate between intra
pair and extra pair young and therefore cares for any offspring
of his pair-partner,so as not to jeopardize the survival
of his own young. Alternatively, paternal care of extra pair
young could be an indicator for male quality or simply a tactic
to maintain his bond with the female and so securing future
mating possibilities in such a long-lasting relationship (Fietz
and Dausmann, 2003). Genetic analyses showed that the
male ("social father") of our observation was indeed only the
genetic father of one offspring, but not the other (Schwensow
et al., 2007). However, even if he was able to distinguish
kin from non-kin, he should still have defended the tree hollow
in order to protect his one own offspring.Interestingly,in
the weeks before these observations, the male and the
female had always spent the daily resting period together in
the same tree hollow. However, the day after the predation
attempt they slept apart, the male in the old, and the female
together with the offspring in the new tree hollow. We
cannot judge whether the male was unable to find the female
in the new tree hollow, whether he chose to rest in the old
hollow,or was prevented from entering the new tree hollow.
Conclusion
Clearly,the surveillance of offspring either directly within the
tree hollow (additionally offering thermoregulatory advan-