Yellowstone Wolf Packs
Three decades after 14 wolves were released in 1995, Yellowstone’s population has cycled through 53 named packs. Here is the full history — population, pack evolution, territories, and mortality — from 30 years of NPS reports.
Population history, 1995–2024
Growth was rapid in the first decade, peaking at 272 wolves in 2002. Since then the population has settled into a lower but stable range as the available territories filled and natural mortality (chiefly wolves killing wolves) balanced reproduction.
Every documented pack
Packs below are listed by how long they’ve been recorded. “Years active” counts the years a pack appears in the NPS reports — gaps mean the pack wasn’t recorded that year.
| Pack | First recorded | Last recorded | Years active |
|---|---|---|---|
| Lamar Canyon | 1995 | 2024 | 30 |
| Yellowstone Delta | 1995 | 2024 | 30 |
| Mollie's | 1995 | 2024 | 28 |
| Slough Creek | 1995 | 2024 | 28 |
| Cougar Creek | 2001 | 2024 | 24 |
| Bechler | 2002 | 2024 | 23 |
| Druid Peak | 1995 | 2020 | 21 |
| Hayden Valley | 1997 | 2020 | 21 |
| Leopold | 1995 | 2020 | 21 |
| Soda Butte | 1995 | 2023 | 20 |
| Nez Perce | 1995 | 2019 | 19 |
| Teton | 1995 | 2021 | 19 |
| Butte | 1995 | 2024 | 18 |
| Canyon | 2000 | 2024 | 18 |
| Crystal Creek | 1995 | 2019 | 18 |
| Madison | 1995 | 2023 | 18 |
| Hellroaring Creek | 1997 | 2023 | 17 |
| Rose Creek | 1995 | 2019 | 17 |
| Swan Lake | 1997 | 2015 | 17 |
| Thorofare | 1995 | 2024 | 15 |
| Bighorn | 1997 | 2024 | 14 |
| 8 Mile | 2009 | 2024 | 13 |
| Agate Creek | 2002 | 2020 | 13 |
| Gibbon | 2003 | 2022 | 13 |
| Junction Butte | 2012 | 2024 | 13 |
| Absaroka | 1995 | 2009 | 12 |
| Chief Joseph | 1995 | 2015 | 12 |
| Geode Creek | 1999 | 2021 | 12 |
| Snake River | 1997 | 2020 | 11 |
| Wapiti Lake | 2015 | 2024 | 10 |
Showing the 30 longest-lived of 53 documented packs.
What kills Yellowstone wolves?
In 2024, the most recent year with a breakdown, NPS recorded 17 known deaths. The leading cause was human: human-caused deaths (vehicle strikes, legal management removals, and illegal take). Human-caused mortality is one of the few causes a recovered population cannot regulate on its own.
See each pack’s territory on the wildlife map, or learn where to watch them.
Frequently asked questions
How many wolf packs live in Yellowstone?+
As of 2024, NPS recorded 9 packs inside Yellowstone, totaling 108 wolves. Since reintroduction in 1995, 53 distinct packs have been documented forming, splitting, and dissolving over time.
Which Yellowstone wolf pack has lasted the longest?+
Lamar Canyon has one of the longest recorded spans, active from 1995 through 2024. Pack continuity is rare — most packs form, shift territory, and dissolve within a decade as alpha animals die or disperse.
Why did the wolf population decline from its peak?+
The population peaked at 272 in 2002 and has since regulated downward to around 108. The primary natural cause is intraspecific strife — wolves killing wolves from rival packs. This is normal for a recovered, territory-competitive population.
How do wolf packs form and split?+
New packs form when dispersing wolves leave their natal pack, find a mate, claim a territory, and breed. Packs split when a group breaks away to form a new pack, or dissolve when alpha animals die. The NPS record tracks these events where reported.
Where can I see which pack is which?+
Open the interactive wildlife map to see each pack's most recent territory polygon, or read where to see wolves for the northern-range packs most often visible to visitors.
Sources & data notes
- Pack list and spans: NPS Annual Wolf Reports (1995–2024), canonicalized for name aliases.
- Population and mortality: NPS Annual Wolf Reports.
- Lineage (parent/child packs) is sparsely populated in the source data; pack spans are reliable but family trees are not.
- NPS Yellowstone Wolf Project Report 1995-1996 — National Park Service (Values may be parsed or inferred from annual report text.)
- NPS Yellowstone Wolf Project Report 2002 — National Park Service (Values may be parsed or inferred from annual report text.)
- NPS Yellowstone Wolf Project Report 2024 — National Park Service (Values may be parsed or inferred from annual report text.)
- NPS Yellowstone Wolf Project 95% MCP shapefiles — National Park Service (95% MCP convex polygons include unused area and do not indicate use intensity.)