influence du climat et de la prédation sur l'utilisation de l'habitat et la ...

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2.5. Discussion
Searching
Finding adult porcupines was relatively easy in our study area in spring and at the end of
autumn, when porcupines used open fields to forage. Juveniles were much more challenging
to find . Had we limited to three the number of searches around each mother on a given year,
and to 30 minutes the duration of each search, we would have reduced the total time spent
sem·ching to 48.1 hours and the number of juveniles found per 100 hours of search wou Id
have increased to 33 (16 juveniJes found in 48.1 hours). Hale and Fuller (1996) reported 10
juveniles found after 176 one-hour searches around 23 adult females. Their overall success
rate of 43.5 juveniles per 100 mothers is close to ours. Their searching method and the
number of sem"ches performed before finding each new juvenile was, however, not reported.
Doing a maximum of three 30-minute searches per mother would increase search efficiency
when many potential mothers are available. A greater search effort wou Id still be useful if
few adult females are known and the number offound juveniles must be maximized. We
recommend investing most of the effort searching the first 15 m around the mother,
especially in a dense forest habitat where searching a larger radius is not efficient.
Ascel1aining the reproductive status of females around which the searches are made
might increase success rate ofsearches. We considered a female to be lactating ifsome liquid
COLI Id be manually extracted from nipples. This was not al ways reliable. For example, we
made Il lInsuccessful searches around a female who later proved to be pregnant during these
searches (the twelfth search yielded a newborn porcupine; see Fig. 2.3a). An alternative,
probably better method to determine reproductive status consists in checking nipples after
stimulation of milk release by injection of oxytocin (Roze 1989, Hale & Fuller 1996). We
tried this method in the first stages of our study but abandoned it after a few unsuccessful
tests. We, however, suspect that our lack of experience with porcupine handling biased
negatively this early test.
Capu/ring
The most efficient capture method usually was the dip net. Use of a dip net had already
been repol1ed (Zimmerling & Croft 2001 , Zimmerling 2005) but authors did not describe
equipment nor did they evaluate method efficiency. A single experienced observer can safely