Skip to main content

Data from: Harvest of transboundary gray wolves from Yellowstone National Park is largely additive

Cite this dataset

Cassidy, Brenna et al. (2024). Data from: Harvest of transboundary gray wolves from Yellowstone National Park is largely additive [Dataset]. Dryad.


Large carnivores are globally threatened due to habitat fragmentation and loss, prey depletion, and human exploitation. Human exploitation includes both legal and illegal hunting and trapping. Protected areas can create refugia from hunting and trapping, however, hunting can still threaten wide-ranging large carnivores when they leave these areas. Large carnivore reintroductions to protected areas are often motivated to restore ecological processes, including wolf reintroduction to Yellowstone National Park (YNP). Determining if harvest is compensatory or additive is essential for informed conservation strategies, as it influences the overall impact on wolf populations and their ecosystems. If the harvest was compensatory, then increasing harvest pressure outside YNP should not decrease overall survival for transboundary wolves. Alternatively, if increasing harvest was additive, then increasing harvest pressure outside YNP should decrease overall survival for transboundary wolves. We tested the effects of variable harvest pressure following delisting on the survival of YNP gray wolves (Canis lupus) from 1995 to 2022. We defined three harvest levels: no harvest, harvest with limited quotas, and unlimited harvest. We used Cox-proportional hazards models and cumulative incidence functions to estimate survival rates, factors affecting survival, and cause-specific mortality between these three harvest periods to test predictions of the additive mortality hypothesis. Most wolves that primarily lived in YNP were harvested adjacent to the park border. Cox-proportional hazards models revealed that mortality was highest during years of unlimited harvest during winter outside YNP. Cause-specific mortality analyses showed that natural mortality from other wolves and harvest were the two leading causes of death, but that harvest mortality had additive effects on wolf mortality. Wolf survival decreased with increased harvest mortality, while natural mortality remained relatively unchanged. High rates of additive harvest mortality of wolves could negatively impact wolf survival in YNP. Harvest mortality of transboundary wolves is additive possibly due to source-sink dynamics of uneven spatial susceptibility of wolves to harvest mortality across protected area borders, as well as effects of harvest on complex social dynamics of wolves in YNP. Transboundary management of large carnivores is challenging, yet cooperation between agencies is vital for wolf management in and around Yellowstone National Park. Our results support the use of small quota zones surrounding protected areas, that minimize transboundary mortality impacts on large carnivores living primarily inside protected areas.

README: Harvest of Transboundary Gray Wolves from Yellowstone National Park is Largely Additive

These data are the files needed to reproduce results in Cassidy et al. (2024), including survival modeling and cumulative incidence function results.

Description of the data and file structure

Biological Year: biological year starting on September 1 and ending on August 31 of the following year

Wolf Count: the number of Yellowstone National Park resident wolves on December 31

Wolf ID: unique wolf ID number

Color: coat color of wolf, only black or gray

Date: date of capture, GPS location, VHF visual location, or mortality

Mortality Cause: cause of mortality (details of mortality causes can be found in the manuscript)

Entry Type: type of entry (Capture = capture of wolf, GPS = location from GPS collar [one random per day], Mortality = death of wolf, VHF = location from VHF signal with visual confirmation of location by staff)

In Park?: dummy-coded variable if a wolf is in or out of Yellowstone National Park (1 = out park, 0 = in park )

Harvest Level: dummy-coded variable indicating the harvest level occurring in the states outside Yellowstone National Park (2 = quoated harvest, 1 = unlimited harvest, 0 =  no harvest)

Age Class: dummy-coded variable of age class (2 = old adult [>6 years old], 1 = adult [2-5 years old], 0 =  pup or yearling [<2 years old])

Season: (Summer = February 1-August 31, Winter = September 1-January 31)

Predicted Elk Count (10^-3): annual predicted elk abundance from a discrete time Gompertz state-space model (Tallian et al. 2017)

Covariate Interactions: Covariate interactions were created by combining Harvest Level and Season, as well as Harvest Level and In Park.

Missing data code: NA


National Science Foundation, Award: 36630

National Science Foundation, Award: DEB-06137730

National Science Foundation, Award: DEB-1245373

Yellowstone National Park

Yellowstone Forever

University of Montana, Wilderness Institute Meier Graduate Research Fellowship

University of Montana

Living With Wolves