Abstract 313 - New non-invasive method with camera trapping provide data on wild Andean bear body size in Peru
Denisse Mateo, San Diego Zoo Wildlife Alliance / University of San Francisco Quito StudentHall C
Denise Mateo, Russell C. Van Horn, Rebecca Zug
Individual bears vary in body size and condition, which reflect habitat quality, and can influence
their ability to reproduce. Most reports of body size and condition are from direct manipulation
of black bears, brown bears, and polar bears. However, Andean bears are challenging to
capture, and hunting is banned, so there are few direct measures of wild Andean bears. We
present a new non-invasive method to collect body measurements of wild bears from camera
trap photos and videos using horizontal and vertical visual size guides. We demonstrate this
method using data from imagery collected from December 2021 - May 2022 at 3300-3453 masl
in the Manu Biosphere Reserve of SE Peru. As paired cameras were installed there, grid guides
were photographed. In a subset of 149 photo/video sequences, we identified 19 individuals; 13
sequences provided data of known bears of known sex (n=8): 7 males and 1 female. Using the
program ImageJ, we measured 10 body dimensions and repeated each measurement 5 times,
to assess user error. Of those dimensions, we here present one index of body size, horizontal
body length (HBL), and one index of body condition, dorsal-ventral height (DVH), for male and
female bears. Males were on average 17% longer than the female: male HBL averaged (±SD)
127cm (±27.3, 86.8-155.5cm), while the female’s HBL was 105cm (±0.9). Bartareau’s (2017)
data measured directly from American black bears showed that males were on average 11%
larger than females (163.4cm vs 146.1cm) but were 23% longer than the males in our data. The
DVH of male Andean bears was on average 32% larger than the female’s: 40cm (±7.51, 28.9-
46.8) versus 27cm (±1.2), suggesting that males may have been in better condition. We
continue to collect data in this landscape, and in other areas of Peru, to compare data from
bears within and among populations. This method also illustrates a potential use of photos
from other mammal species that are difficult to capture.
