Electronic Supplementary material
In this supplementary material, we present details on the heuristic random travel model, as
well as further analysis according to the mouse lemurs´ travel speed.
A. Heuristic random travel model
1. Material and Methods
We used the heuristic travel model developed by Asensio et al. [1] to test whether mouse
lemurs used a straight line travel in a random direction for searching food. For that purpose,
we estimated the efficiency of finding keystone food resources (preferred food sources) using
a heuristic model and compared it to the observed mouse lemur´s efficiency.
In this model, a route began from the starting point of a mouse lemur’s route and continued in
a straight line in a random direction until it encountered a keystone food resources (preferred
food source) using a given detection distance of visibility or hit the border of the MCP home
range (e.g. [2] for MCP calculations). A new route segment was then calculated in a 360°
random direction from the previous location until it again detected a new keystone food
resources (food source). This was repeated until the total route distance simulated by the
model was equal to the observed mouse lemur’s travel distance for that night. Since detection
field of keystone resources is unavailable for mouse lemurs, we performed calculations using
3 distance categories: 5 m, 10 m and 20 m (see route simulation in Figure 1 for a detection
distance of 5 m).
We used the same efficiency index as defined by [1] to evaluate the search efficiency of our
model.
Efficiency= ((number of food sources visited by the lemur – number of resources found by
the random model)/total number of resources into the home-range.
The efficiency index ranges from -1 to +1, negative efficiency values mean that the random
search model is performing better than mouse lemurs, whereas positive values mean that the
mouse lemurs are more efficient.
This index was calculated for each of the 14 routes analysed using the CPT and containing ≥ 1
directional change (5 animals; 2-3 routes per animal). Efficiency index was compared
between the 3 detection distances using a Friedman test.
B. Travel speed
1. Material and methods:
We assessed the initial travel speed (= distance from the starting point to the waypoint 10
minutes thereafter: 10 min) and final travel speed (= distance between the end of the route
segment (i.e. route between two targets) and a waypoint at 10 min before for each route
segment) and calculated the mean and standard deviation for each individual.
2. Results:
Lemurs did not show any significant difference between their initial and final travel speed (5
m/min; range: 3.7 – 5.8 m/min; Wilcoxon pair-matched test, N=9, Z=-0.917, T=11.50,
p>0.05). However the initial speed was significantly higher in the first than in the last route
segment of a travel (Wilcoxon pair-matched test, N=9, T=2, p=0.012).
3. Discussion:
Mouse lemurs moved faster at the beginning of their foraging activity probably due to a
higher motivation to search for food but do not show an increase in travel speed when close to
keystone resources as do monkeys and apes [3]. However, detecting fine variation in travel
speed on small-scale was challenging due to the used technique and difficulties to keep
constant contact to a small nocturnal animal in dense vegetation. Miniature GPS emitters, now
available, may allow to overcome this problem in the future and to correctly assess variation
in the travel speed.
References
1.
Asensio, N., Brockelman, W.Y., Malaivijitnond, S., and Reichard, U.H. 2011 Gibbon
travel paths are goal oriented. Animal cognition. DOI 10.1007/s10071-010-0374-1
2.
Radespiel, U. 2000 Sociality in the gray mouse lemur (Microcebus murinus) in
northwestern Madagascar. Am J Primatol 51, 21-40.
3.
Janson, C.H. & Byrne, R. 2007 What wild primates know about resources: opening up
the black box. Animal Cognition 10, 357-367.
Figure 1. Example of a heuristic search with a detection distance of 5 m to detect keystone
resources within one mouse lemur´s home range. The grey plain line represents the border of
the home-range. Keystone resources are represented by triangles. The detection area of each
keystone resource (here 5 m) is represented by greyish circles. The plain circle represents the
sleeping site and start location of the route. The black plain line represents the observed route
of a mouse lemur and the black dashed line represents a route simulated by the model. Note
that in this simulation, the mouse lemur found 14 keystone resources while the model found
only 3 resources.