Managing hybridization of a recovering endangered species: The red wolf Canis rufus as a case study

Abstract

Hybridization presents a unique challenge for conservation biologists and managers. While hybridization is an important evolutionary process, hybridization is also a threat formany native species. The endangered species recovery effort for the red wolf Canis rufus is a classic system for understanding and addressing the challenges of hybridization. From 1987?1993, 63 red wolves were released from captivity in eastern North Carolina, USA, to establish a free-ranging, non-essential experimental population. By 1999, managers recognized hybridization with invasive coyotes Canis latrans was the single greatest threat to successful recovery, and an adaptive management plan was adopted with innovative approaches for managing the threat of hybridization. Here we review the application and results of the adaptive management efforts from 1993 to 2013 by comparing: (1) the numbers of wolves, coyotes, and hybrids captured, (2) the numbers of territorial social groups with presumed breeding capabilities, (3) the number of red wolf and hybrid litters documented each year and (4) the degree of coyote introgression into the wild red wolf gene pool. We documented substantial increases in the number of known red wolves and red wolf social groups from 1987–2004 followed by a plateau and slight decline by 2013.The number of red wolf litters exceeded hybrid litters each year and the proportion of hybrid litters per year averaged 21%. The genetic composition of the wild red wolf population is estimated to include < 4% coyote ancestry from recent introgression since reintroduction. We conclude that the adaptive management plan was effective at reducing the introgression of coyote genes into the red wolf population, but population recovery of red wolves will require continuation of the current management plan, or alternative approaches, for the foreseeable future. More broadly, we discuss the lessons learned from red wolf adaptive management that could assist other endangered species recovery efforts facing the challenge of minimizing hybridization.

Space Use and Habitat Selection by Resident and Transient Red Wolves (Canis rufus)

“…The USFWS Recovery Program conducted annual trapping to capture and radio-mark juvenile and adult red wolves for long-term monitoring and management of the reintroduced population [23,39–40]. We assisted annual trapping efforts during 2009–2011 to deploy GPS radio collars on red wolves.…”

“…We assisted annual trapping efforts during 2009–2011 to deploy GPS radio collars on red wolves. During this period, the Recovery Program annually monitored 83–94 radio-collared red wolves in 16–17 packs [3,23,40]. Each year, 10–15 radio-collared red wolves not associated with known packs or breeding pairs were assumed to be transient (e.g., dispersing) [41].…”

“…We identified resident pairs of red wolves as radio-collared individuals of breeding age (≥2 years old) that were temporally and spatially associated with one another and defending a territory for ≥4 months as a breeding pair [3,33]. Recovery Program biologists confirmed breeding pair status during spring den work by locating dens and daybeds of radio-marked females to verify and obtain pup counts for each radio-collared breeding pair [23,39–40,46–47]. We also classified non-dispersing juveniles fitted with radio-collars as residents.…”

Who’s your mama? Riverine hybridisation of threatened freshwater Trout Cod and Murray Cod

“…Although hybridization is a natural process and is relatively more common in fishes than other vertebrates, the occurrence of hybridization and introgression poses some real challenges for threatened species recovery programs (Gese et al, 2015). Reintroductions of threatened fish are usually resource limited, and so the number of individuals available from captive breeding programs is often only equivalent to the reproductive output of a handful of wild spawnings.…”

Who’s your mama? Riverine hybridisation of threatened freshwater Trout Cod and Murray Cod

“…373 Although hybridization is a natural process and is relatively more common in fishes than other 374 vertebrates, the occurrence of hybridization and introgression poses some real challenges for 375 threatened species recovery programs (Gese et al, 2015). Reintroductions of threatened fish are 376 usually resource limited, and so the number of individuals available from captive breeding 377 programs is often only equivalent to the reproductive output of a handful of wild spawnings.…”