JACKSON, Wyo. — Mountain goat numbers are down in Grand Teton National Park (GTNP), and removal of the invasive species is ongoing in an effort to reduce impacts on the vulnerable Teton Range bighorn sheep population.
Mountain goats are not native to the GTNP region. According to GTNP officials, which includes Chief of Staff Jeremy Barnum and Park biologists, mountain goats compete directly with bighorn sheep for habitat and forage, “and may displace them from crucial habitat.” Non-native mountain goats can also transmit fatal diseases to bighorns, a population that’s already considered vulnerable by the Teton Bighorn Sheep Working Group due to human development and resulting loss of habitat and migration pathways.
“If the NPS does not continue to actively manage non-native mountain goats as outlined in the management plan, the population will grow and the threat of competition and pathogen transmission will increase again,” GTNP officials tell Buckrail.
The 2019 Non-native Mountain Goat Management Plan/Environmental Assessment outlines the removal of mountain goats from the Park with the use of lethal and/or non-lethal methods. Non-lethal methods include capture and relocation; however, GTNP states that they have faced challenges in securing locations and collaborations with other agencies for capture and relocation. This hesitancy is attributed to low past capture success, costs and known disease history of the source population of GTNP’s mountain goats.
GTNP officials confirm that 15 non-native mountain goats were lethally removed from the Park in 2023. Currently, the rough estimate of non-native mountain goats in the Teton Range is 10 to 20 goats.
“Managing mountain goats in the park will be an ongoing process,” GTNP officials say. “Our goal is to keep the mountain goat population to a level where impacts on the native bighorn sheep are likely minimal. Because the goats can continue to move into the Tetons from nearby areas, permanent eradication may not be achievable.”
At this time, the low number of mountain goats are unlikely to put much pressure on bighorn sheep. However, GTNP officials say that review of final lab results from a 2019 to 2022 intensive population monitoring study suggests the Teton Range bighorn sheep numbers did decrease last year.
“We are in the process of analyzing this dataset to estimate population size for those years,” GTNP officials share. “However, we have reason to think that the Teton Range bighorn sheep population declined in 2023 because of the severe winter.”
The Wyoming Game and Fish Department’s total aerial survey count of Teton Range bighorn sheep in April 2023 was 71. GTNP officials call this a “marked decrease” from the 2020 to 2022 counts, which ranged from 90 to 104 bighorn sheep.
GTNP officials note that, while aerial surveys are helpful in tracking trends of wildlife populations over time, their results do not reflect the census of a population. The 2019 to 2022 monitoring study mentioned above is aimed at estimating the true population size of the Teton Range’s bighorn sheep and comparing that to minimum population size determined from the aerial surveys.
An aerial survey of bighorn sheep has not been conducted yet in 2024.
