Mexican wolf (Canis lupus baileyi)
Chris Wiese, Mike Phillips, Cassidi Cobos
Ladder Ranch, NM
US Fish & Wildlife Service
Once common throughout portions of Arizona, New Mexico, Texas, and Mexico, human persecution resulted in the extirpation of Mexican wolves in the wild. Current challenges include political pressures against wolf releases, illegal shootings, and lack of space for population expansion. Additionally, due to the small founder population, diminished genetic diversity appears to be affecting the fecundity and survival of wolves in the wild. Limited pen space in the captive breeding program restricts the size and reproductive output of the captive population.
- Listed as endangered in portions of AZ, NM where this wolf subspecies is known to occur except: Experimental Population (Nonessential): portion of AZ north of I-10 and south of I-40; portion of NM north of I-10 (in west), north of the NM-TX border (in east), and south of I-40.
We aim to contribute to recovery of Mexican gray wolf populations in the wild in the US and Mexico.
Over the next five years, TESF will continue to support Mexican Gray Wolf recovery by providing a captive facility on the Ladder Ranch that houses up to 25 wolves at any one time, including breeding pairs and wolves transitioning between the wild population and captivity. The Ladder Ranch facility will respond to the needs and overall project goals set by the USFWS and the Species Survival Plan on an annual basis.
Supporting Rationale for Objective
The Ladder Ranch has been actively involved in Mexican Gray Wolf recovery since 1997, beginning with construction of the Ladder Ranch wolf management facility (LRWMF). As one of only three pre-release facilities nationwide, the LRWMF plays an important role in the USFWS’s implementation of wolf reintroductions to the wild by providing pre-release care and acclimatization for animals eligible for release to the wild. The LRWMF also assists with specific management needs associated with reintroductions in the Blue Range Wolf Recovery Area by serving as a “halfway house” between the wild and traditional holding facilities (zoos and wildlife sanctuaries) for wolves that are removed from the wild for medical reasons or for depredating livestock. The LRWMF is managed collaboratively by TESF and the USFWS. Since we began housing wolves in 1998, over 140 different wolves have passed through the LRWMF facility.
As a member of the Mexican wolf species survival plan (SSP), we adhere to the management guidelines that standardize captive management in both the US and Mexico. The mission of the SSP is to contribute to Mexican wolf recovery through captive breeding, public education, and research. The SSP uses several criteria to determine the eligibility of a wolf for release. These include: genetic makeup in relation to both captive and wild populations (i.e., “surplus” to the captive community and underrepresented in the wild), reproductive performance, behavior, and physical suitability. It is critically important that release candidates exhibit natural behaviors, especially fear and avoidance of humans. We therefore take steps to prevent socializing or habituating the wolves housed at the LRWMF to minimize conflict with humans once released into the wild. In accordance with SSP recommendations, we reinforce the wolves’ natural avoidance behavior to humans by providing as much privacy and as little disturbance as possible. This includes minimizing the length of time an animal is held in captivity and minimizing contact with humans during husbandry and maintenance events (i.e., we feed only once or twice a week and we spend as little time as possible inside the wolf pens during husbandry and maintenance).
Mexican gray wolves (MGW) are a distinct subspecies of gray wolves that roamed most of the southwestern US and portions of Mexico until they were functionally eradicated in the wild through aggressive government-sponsored predator control measures. By the time the Mexican gray wolf was listed as endangered under the ESA in 1976, it was on the verge of extinction. Wildlife biologists captured the last five wolves remaining in the wild and began a captive breeding program. As a result, the subspecies is now secure in captivity.
Reintroductions of MGWs into the Blue Range Wolf Management Area (BRWMA), which spans portions of eastern Arizona and western New Mexico began in 1998, and reintroductions in Mexico began in 2011. About 110 wolves were free-ranging in the BRWMA and ~25 in Mexico in 2017.
Project Activities in 2018
A total of 15 different wolves were held at the LRWMF in 2018, with a maximum of 14 at any one time.
Feedings: Mexican gray wolves held at the LRWMF are fed a combination of foods recommended by the SSP. These are: Mazuri® Exotic Canine Diet (aka “kibble”), Central Nebraska classic canine diet (aka “carnivore logs”), and native prey species. Mazuri® Exotic Canine Diet is a meat-based kibble diet preferred by most zoos that meets the nutrient requirements of all wolf life stages. Carnivore logs are composed predominantly of horsemeat and fortified meat byproducts that are frozen into 5-pound logs. These are protein-rich and also suitable for all life stages. Prey animals (mule deer, oryx, elk, rabbits, and bison) are mainly provided as meat scraps and/or bones salvaged from road-kill or from hunts on the Armendaris and Ladder Ranches and are sporadically fed as supplemental food.
Water: The water that supplies the wolf pens is first pumped from a warm spring in Animas Creek into a 5,000-gallon holding tank by a piston pump. Water from the holding tank is then used to fill (by gravity) smaller holding tanks (500 or 2,500 gallons, respectively), which in turn are used to provide water to the wolves in one or two 50-gallon tubs placed in each wolf pen. Furthermore, we installed and used a drinker (shallow and close to the ground) in pen 1 to give the pups access to water (they cannot reach the water in the 50-gallon troughs; all wolves in pen 1 were seen using the drinker). The 50-gallon tubs are cleaned and/or topped off regularly to ensure that all wolves have access to fresh water at all times. In addition, we occasionally treated the water in the secondary holding tanks with very dilute bleach (> 1:2,000, which is the dilution used to treat well-water for human consumption) to prevent algal growth.
Observations: We observed animals from the blind on a regular basis to monitor their overall health, behavior, and wellbeing. In addition, we observed daily (or twice daily) from the blind when wolves first arrived at the facility, during the breeding season, and around putative whelping times. Informal observations took place during scheduled feedings, where we obtained a visual of animals in the facility and checked for signs of injury or illness. In addition, we made regular use of trail cameras to get close-up views of individual wolves.
Health Checks: All wolves received thorough health checks, vaccinations, and anti-parasite medication before arriving at the LRWMF. Similarly, all wolves leaving the LRWMF in 2018 received deworming and anti-parasite medication (ivermectin, revolution, and/or praziquantel) before their departure from the facility and received vaccinations as warranted. The goal is to perform health checks and update vaccinations for each wolf once a year (usually done during the cooler months). All wolves in the facility at the end of December 2018 were current on their vaccinations and treatments.
Oral ivermectin treatment for heartworm prevention: We continued a regimen of once-a-month oral ivermectin treatment of all wolves to prevent heartworm. We followed the protocol developed for and approved by the MGW SSP.
Semen collection: All male wolves present in the facility (M1384, M1400, M1336, mp1602, and mp1603) were captured and processed for semen collection on February 8, 2018. The semen collections were performed by Dr. Cheryl Asa and Karen Bauman, and were overseen by Dr. Susan Dicks.
Breeding season: Two pairs of wolves were introduced (F1431 and M1400) or remained together (F1323 and M1336) at the LRWMF during the breeding season 2018, in the hopes that one or both pairs would produce pups that could be cross-fostered into the wild in 2018.
Proposed Future Activities
As one of only three pre-release facilities in the country and the facility closest to the wild BRWMA population, the SWMF, and Mexico, the LRWMF plays an important role as a transitional facility for wolves that are being transferred between captivity and the wild. This includes wild wolves that need to be moved to captivity due to livestock depredations, as well as releases of captive-bred wolves to support the wild population.
Cross-fostering is a technique in which very young pups (less than 10 days old, i.e. before they can see or hear) from genetically desirable captive wolf pairings are swapped or introduced to denning wild wolf parents. This technique eliminates concerns of captive-born wolves habituating to humans because pups are introduced to the wild prior to their being able to perceive sights and sounds. Cross-fostering has been used successfully to increase the genetic diversity of red wolves in North Carolina and has also been tested in European gray wolves. Moreover, it has been used successfully in 2014, 2017, and 2018 to place captive-born MGW pups into the den of a wild wolf pack that was known to rear young that avoid conflict with humans.
Because the Mexican wolf holding facilities are currently at capacity, not all captive wolves are allowed to breed. In turn, this means that not all wolf-holding facilities participate in the breeding program. Breeding pairs are carefully chosen using several criteria, including genetics, compatibility, and need. Mexican gray wolves produce pups only once a year: they generally breed in February or March and whelp 2-6 pups in April or May. For 2019, the LRWMF will hold one breeding pair whose pups will be valuable to the captive population as well as being candidates for cross-fostering efforts.
In this way, we will continue our strong support of the USFWS-led efforts to recover the MGW in the Southwest. In 2019, we plan to continue to serve as caretakers of important wolves, participate in hands-on activities (captures, health checks, transfers, surveys, etc.) and mandatory training sessions, and participate in SSP-related management activities (for example, annual meetings).