Wolf Pack Dynamics (Preliminaries) Virginia Stoll Wm. D. Stone

A Mexican Lobo

The ‘Lobo’ • Smallest subspecies of North American Gray Wolf • 50 – 80 pounds • ~30 inches at the shoulder • Original range much of Mexico, NM, AZ

History • Almost extinct by mid-20 th century • Listed as endangered 1976 • Recovery effort started 1977 • Small population captured in Mexico • Two small captive populations • 7 founders.

Wolf Packs • Basic unit of population – the pack – One alpha pair • Normally the only breeders – Young adults • Help hunt and baby-sit – Pups

Formation of new packs • Young adults can leave the pack – become ‘lone wolves’ • New packs can be formed by a pair of lone wolves joining up • Very large packs can split • Death of one of the alpha pair can cause pack to split

Pack size • Prey – Size • Mostly elk – Availability • Lots of elk • Scavengers – Ravens • Can eat 2 lbs. of meat per day each

Population Pressures • In the New Mexico re-established wolf population, two largest sources of adult mortality are – Cars – Illegal shooting

Natural Mortality • Food pressure mostly affects survival of pups to weaning • Inter-pack battles can be a significant cause of death

Genetics • Starting with tracking one locus, with one marked gene in a single individual • Probability of duplicate copies in an individual • (comparative only)

Input from Federal Wolf Biologists • New Mexico packs rarely are larger than a breeding pair plus pups – Subspecies difference?

– Growth stage vs. steady state?

• So far, little food or territory pressure

Genetics • US Fish & Wildlife has full genetic profiles of every wolf they have handled • Very small number of founders • Selective breeding for genetic diversity • They hope our model can help

Model Results

Wolf P opulation

160 140 120 100 80 60 40 20 0 0 20 40 60

Ye a r

80 100 120

Female with pups