|Carlos A. Lopez Gonzalez|
|Black bear (Ursus americanus) Ecology, Conservation and Management in the State of Sonora, Mexico|
|Location: State of Sonora, Mexico|
|Species: Mexican black bear (Ursus americanus)/Carnivores|
|Abstract: This proposal seeks funding to determine home range, habitat use, and food habits of endangered Mexican black bears in the mountainous State of Sonora, Mexico for the 2005-2006 field seasons. Results of this research will illuminate the conservation needs for this species of large carnivore at the southern limit of its distribution in an area where temperate and tropical species overlap to form unique biological communities. This project proposes an investigation of bear habitat use through radio-telemetry and food habits through scat analysis. In this region of Mexico where ranching is the primary land use, the new information will help us understand the ecological bases for bear-livestock conflict. Results from the research will be useful to wildlife and land managers in Mexico, as well as planning for the conservation of black bears and associated biodiversity.|
Project Update: March 2006
The site is located in the Sierra San Luis, Sonora, Mexico. The area is covered by pine forests, pine-oak forests, pine-oak forests with second growth, open low forest, and grasslands. Other large carnivores currently found here include mountain lions and jaguars. The area is characterized by a rugged topography, a primitive network of roads making it one of the last remaining wilderness areas of northern Mexico, but without protected status.The area lacks any human settlements and is characterized by large ranching operations with free ranging livestock.
Two adult males were captured, measured and fitted with radio-transmitters during late April. The bears were regularly tracked to determine home range size, habitat use and activity patterns.
Partial estimates of home range to date, using adaptive kernel estimators are 400 (± 200) km². No further analyses have been done at the time of this report.
Habitat use and activity patterns
Black bears were recorded using six habitat types in the region, they were most frequently recorded at open low forest (41.2%), followed by pine forest (31.4%), and pine-oak forest (15.4%). Significant differences were found between ranches, as bears were only recorded in three of the six habitat types. Bears were recorded active mainly during daylight hours, with two peaks of activity one after sunrise and the other before sunset.
Population structure and density
The structure of the bear population was determined through camera trap records, which identified a composition of 30% adults, 16.7% cubs and 53.3% subadults. Individual markings were used to estimate a density of 16 bears. A total of 422 records were obtained between April and December within the study area. Only 73 records were obtained from Rancho Los Ojos, and the majority, (349) were from Rancho El Pinito. Records break down as such: 141 camera trap records, 175 scats, 102 sets of tracks, two resting sites, and two sightings.