Vol. 15 - Deutsches Primatenzentrum

Lemur News Vol. 15, 2010 Page 17
ence of a boiidae snake later identified as Sanzinia madagascariensis.
I saw two white-footed sportive lemurs (Lepilemur
leucopus),one located at 4m height and the other at 5m
height in a tree over the trail.The sportive lemurs were barking
and looking at the snake. The snake was moving at
approximately 4 m high in a tree and was attempting to cross
a gap and move into a tree nearer to the tree in which the
sportive lemurs were located.The attempt was unsuccessful
as the snake slipped and almost fell out of the thin, terminal
branches. The snake then moved down to 3.5 m height and
began crossing the canopy gap along thicker branches. The
sportive lemurs continued to alarm bark at the snake until
21:02 when the snake turned away from the gap in the
canopy and began moving lower down in the tree and away
from the sportive lemurs. The sportive lemur alarm calling
ended by 21:04 when the snake had traveled down the tree
trunk to 3m in height. The sportive lemur lowest in the tree
continued to watch the snake while the other sportive lemur
moved to 8m height in its tree and began feeding.
At 21:15, I was preparing to leave the area when I noticed a
mouse lemur at 0.5 m in the same tree as the snake. The
snake was at 3 m height in the tree and moving down the
main trunk of the tree. The mouse lemur looked at me as it
walked up the main trunk of the tree in the direction of the
snake. The snake faced the mouse lemur, but the mouse
lemur did not appear to notice the snake as it alternated
looking in my direction with looking around its immediate
area while foraging for insects. The mouse lemur continued
to move up the tree until it was within 0.25 m of the snake
where it paused and looked intently at the spot where the
snake was located and then jumped backwards away from
the snake. The mouse lemur then began moving around the
tree at the same height (3 m) as the snake,jumping to terminal
branches,and running along main branches while pausing
to look at the snake. The mouse lemur’s movements took it
from 1m to only a few cms in distance from the snake. The
mouse lemur continued this pattern of running and pausing
to examine the snake for 7 mins. The mouse lemur then began
foraging for insects in a neighboring tree at 3-4 m height
and within 1-2 m of the snake. While foraging, the mouse
lemur would pause to look in the direction of the snake
which remained motionless.The mouse lemur foraged in this
manner for 4 mins until a sportive lemur alarm called. Prior
to the alarm call, the mouse lemur was foraging approximately
1m from the snake and the snake began moving down
the tree trunk.At the sound of the sportive lemur alarm call,
the mouse lemur jumped to 2 m distance from the snake and
paused in its foraging to watch the snake. The snake remained
motionless.A minute later the sportive lemurs alarm
called again. The snake began moving down the trunk of the
tree again and the mouse lemur moved to forage insects in
trees that were approximately 3-5 m from the snake and at
5m height.After 5 mins of foraging at this increased distance
from the snake, the mouse lemur moved back into the tree
where it was initially observed and foraged within 1m of the
snake for 2 mins. The mouse lemur then moved close to the
snake coming within less than 1m of the boa and running and
jumping around the snake while pausing to watch it while
standing bipedally. After 3 mins of remaining motionless
while the mouse lemur ran, jumped and watched the snake,
the snake began moving back up into the dense crown of the
tree. The mouse lemur continued running and jumping
around the snake and watching it at a distance of 0,5-1 m
away as the snake moved into the crown of the tree. 8 mins
later,the mouse lemur began foraging insects at 3-4 m height
in the canopy and within 0,5-1 m from the snake with occasional
glances in the direction of the snake.The mouse lemur
then moved further away from the snake and foraged insects
at 5m in height and approximately 5 m distance from the
snake.At 21:46 the mouse lemur was out of sight and did not
return by 21:51 when I left and continued the mouse lemur
walk.A return visit to the location at 10:05 for species identification
of the species revealed the presence of no mouse lemurs
or Lepilemur in the vicinity.
Discussion
Eberle and Kappeler (2008) describe the successful mobbing
of a Sanzinia madagascariensis by two female and one male
mouse lemur (Microcebus murinus). The mobbing caused the
snake to release a captured male mouse lemur. Subsequent
genetic analysis revealed that the mobbing females were related
to the attempted victim (Eberle and Kappeler, 2008).
Additional encounters between mouse lemurs and snakes
without captured prey did not elicit mobbing behaviors from
the mouse lemurs (Eberle and Kappeler, 2008). Instead, the
mouse lemurs sat approximately 2 m from the snake and
watched it. (Eberle and Kappeler, 2008). The mobbing of the
snake by relatives of a captured mouse lemur and the lack of
mobbing behaviors by solitary mouse lemurs in Eberle and
Kappeler’s study support the kin selection hypothesis for the
evolution of mobbing behaviors. However, the solitary
mouse lemur observed in this study displayed mobbing-like
behaviors in the absence of kin or other individuals. Additionally,
under experimental conditions, solitary mouse lemurs
monitored model snakes and even locomoted towards
the model predators (Rahlfs and Fichtel,2010).The presence
of mobbing-like behaviors in solitary animals lends support
to the by-product mutualism hypothesis. Mouse lemurs may
display mobbing-like behaviors as an individual strategy and
then when larger numbers of mouse lemurs contact a predator,
the appearance of a group-defense strategy may result
from multiple individuals pursuing the same strategy.
The observations here also lend support to the perception
advertisement hypothesis.The mouse lemur may have benefited
by displaying mobbing behaviors toward the snake to let
the snake know that it was being monitored and would not
surprise the lone mouse lemur as it foraged.However,a prediction
of the perception-advertisement hypothesis is that
cryptic predators should flee when faced with alarm calls and
mobbing as they cannot surprise prey in their vicinity. The
alarm calling by the sportive lemurs and the mobbing-like
behaviors of the mouse lemur observed in this study did not
cause the snake to flee. Instead, the snake remained in the
area while both the sportive lemurs and mouse lemur left
the area.Size of the mobbing and alarm-calling group may be
important. Tarsiers were more likely to retreat first if their
mobbing group consisted of four or fewer individuals (Gursky,2007).The
small group sizes here may have not caused the
predator to flee,but may have served as an adequate warning
that it had lost the element of surprise and should not
expend energy in an attack.
Of particular interest in these observations was the opportunity
to view the responses of two different nocturnal primate
species to the same predator. Such observations are
infrequent in the literature. Schulke (2001) observed Phaner
and dwarf lemur (Mirza coquereli) together mobbed Boa
manditra. In the case of the sportive and mouse lemurs,
neither showed the same behavioral response to the Sanzinia
madagascariensis. The pair of Lepilemurs maintained a
larger distance between themselves and the snake than did
the mouse lemur. The mouse lemur did not vocalize in the
vicinity of the snake, however, the sportive lemurs vocalized
during their encounter with the snake.Mouse lemurs seldom
respond to predator models with alarm calls in experimental