{"id":792830,"date":"2026-05-13T06:31:19","date_gmt":"2026-05-13T06:31:19","guid":{"rendered":"https:\/\/www.europesays.com\/us\/792830\/"},"modified":"2026-05-13T06:31:19","modified_gmt":"2026-05-13T06:31:19","slug":"disease-outbreak-cuts-wyoming-yellowstone-wolf-numbers","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/792830\/","title":{"rendered":"Disease outbreak cuts Wyoming, Yellowstone wolf numbers"},"content":{"rendered":"

A flare up of a disease that\u2019s especially lethal to wolf pups took a toll on Wyoming and Yellowstone National Park wolf numbers in 2025, reducing biologists\u2019 counts to a level last seen when wolves were still reestablishing following the species\u2019 historic 1995-96 reintroduction<\/a>. <\/p>\n

\u201cIt was the lowest number of wolves in 20 years,\u201d Wyoming Game and Fish Department wolf biologist Ken Mills told WyoFile. \u201cThat was definitely during the population creep stage, so they were still establishing in the state.\u201d <\/p>\n

All signs point toward canine distemper being the primary reason Wyoming\u2019s statewide wolf population plunged to a minimum count of 253 wolves and 14 breeding pairs at the end of 2025, Mills said. <\/p>\n

Distemper was detected in 64% of animals in the northwestern Wyoming zone where wolves are classified as \u201ctrophy game.\u201d While adults can survive the contagious virus, which is a measles-like affliction in canines, it\u2019s \u201cquite lethal\u201d for pups and only an estimated \u201c31 to 34\u201d of the 87 documented born pups lived to the end of the year, a survival rate of just 37%, according to Game and Fish\u2019s 2025 wolf monitoring report<\/a>. <\/p>\n

In the past, distemper was a density-dependent disease that surged when populations were high, Mills said. It last flared up in 2018<\/a>, which wasn\u2019t long after a two-year period where wolves were protected from hunting by the Endangered Species Act and populations \u2014 and conflict<\/a> \u2014 were higher. <\/p>\n

The 2025 flare up was the first time Mills documented lots of distemper when wolf numbers were not particularly high. The occurrence has him searching for alternative explanations.<\/p>\n

\u201cCould it be cyclical? Yeah,\u201d the Pinedale-based biologist said. \u201cHowever, these are potentially eight-year cycles, and it takes a lot of time to collect data and understand what\u2019s going on.\u201d<\/p>\n

There\u2019s cause to believe that distemper will abate in Wyoming wolves this year. When Yellowstone wolves have experienced outbreaks<\/a>, the event lasts a year and then there\u2019s recovery, Mills said. And the Wyoming population now has more antibodies and resistance built up and so is in good shape to recover itself, he said. <\/p>\n

But in 2025, distemper hurt Wyoming wolf numbers, which was a first.<\/p>\n

Before that, \u201cwe really haven\u2019t had a canine distemper outbreak that has caused a population-level effect,\u201d Mills said. <\/p>\n

In 2024, Mills and his biologist counterparts detected 330 wolves and 24 breeding pairs statewide. The estimated 253 wolves and 14 breeding pairs in 2025 means the raw wolf count tumbled by 23% and the reproductive segment fell by 42%. <\/p>\n

Of those, 132 wolves in 22 packs that included 10 breeding pairs dwelled in the mountainous portion of northwest Wyoming in the \u201ctrophy game\u201d area. There were nine wolves in three packs and no breeding detected on the Wind River Indian Reservation. And in the zone where Wyoming manages wolves as predators \u2014 where they can be killed by any means<\/a> without limit \u2014 there were 28 wolves in five packs, including one breeding pair. <\/p>\n

The remainder of Wyoming\u2019s wolves \u2014 84 wolves running in seven packs that included three breeding pairs \u2014 dwelled in Yellowstone National Park, according to the state\u2019s monitoring report. <\/p>\n

The park\u2019s public affairs officers, whose office has been inundated with inquiries about a recent grizzly bear attack<\/a>, did not respond to WyoFile\u2019s request for an interview before this story published.<\/p>\n

The overall number of Yellowstone wolves has dipped into the 80s twice before, in 2012 and 2018. But by other measures, 2025 was a tough year that the park population had not experienced since the reintroduction era. The distemper outbreak appeared to be \u201csynchronous\u201d in Wyoming and Yellowstone, and pup production and survival was also dismal in the national park, Mills said.<\/p>\n

\u201cSeventeen pups survived in Yellowstone,\u201d he said, \u201cwhich was the lowest they ever recorded.\u201d <\/p>\n

Outside of Yellowstone, Game and Fish will consider the lower wolf population when its biologists and wardens are setting fall 2026 hunting seasons (hunting isn\u2019t allowed in the park, though park wolves frequently leave<\/a> ). That proposal isn\u2019t public yet, but Mills anticipates that there will be a \u201csurplus\u201d of animals and a wolf hunting season, even if mortality limits are reduced.<\/p>\n

Wyoming\u2019s relatively few wolves have enabled the state to manage with precision<\/a> and a degree of predictability, although the surge of distemper interrupted a long run of population stability. Still, the unexpected disease outbreak left Mills feeling good about Wyoming\u2019s plan for managing its wolves. <\/p>\n

\u201cWe set up the population objective of 160 wolves to be able to accommodate an event similar to what we experienced, and still meet our minimum recovery criteria,\u201d Mills said. <\/p>\n

That recovery criteria includes 10 breeding pairs outside of Yellowstone in Wyoming\u2019s trophy game area. Mills\u2019 2025 surveys detected exactly 10 packs with pups in that zone. <\/p>\n

\u201cWe met the minimum,\u201d Mills said. \u201cIt actually worked exactly as we intended.\u201d<\/p>\n

___<\/p>\n

This story was originally published by WyoFile<\/a> and distributed through a partnership with The Associated Press.<\/p>\n","protected":false},"excerpt":{"rendered":"A flare up of a disease that\u2019s especially lethal to wolf pups took a toll on Wyoming and…\n","protected":false},"author":3,"featured_media":792831,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[27],"tags":[3425,10106,57,323591,159,21951,61,67,132,68,837,9571,13669,1669,17860],"class_list":{"0":"post-792830","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-wildlife","8":"tag-animals","9":"tag-climate-and-environment","10":"tag-general-news","11":"tag-ken-mills","12":"tag-science","13":"tag-trending-news","14":"tag-u-s-news","15":"tag-united-states","16":"tag-unitedstates","17":"tag-us","18":"tag-wildlife","19":"tag-wolves","20":"tag-wy-state-wire","21":"tag-wyoming","22":"tag-zoology"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/116565867649128250","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/792830","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=792830"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/792830\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/792831"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=792830"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=792830"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=792830"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}