Jorge Servin, Instituto de Ecologia, A.C., Centro Regional Durango, Apdo. Postal No. 632, C.P. 34100, Durango, Dgo., Mexico

Although the Mexican wolf (Canis lupus baileyi) is an endangered species, it has been poorly studied. Here, I report duration and frequency of Mexican wolf chorus howling through the year from a pack of five adults (2 females and 3 males) in captivity in "La Michilia", Biosphere Reserve at Western Sierra Madre in Durango, Mexico. These are the first quantitative howling data reported for the Mexican wolf. Two hundred and eigthy-six chorus howls were recorded between January and December. Chorus howling was most common during the breeding season (January/February) and tended to listen at dusk and sunrise, like in wolves from northern populations. Daily howling chorus varied in frequency between months (p<0.005); in February, choruses ocurred 2.25 per day with a duration of 59.2 ± 6.6 sec, whereas in August, 0.85 chorus per day and duration of 26.7 ± 3.46 sec was recorded. The mean duration of chorus 41 ± 9 sec for this wolf pack, was shorter than those reported from wolf packs of the northern United States and Canada. Hence, group howling range varies among wolves in Canada, U.S.A. and Mexico.