Dr. Brenna Cassidy — Colorado Parks and Wildlife’s Wolf Monitoring and Data Coordinator — spends many of her days carefully analyzing wolf movements. Her efforts have included everything from monitoring GPS points to being out in the field physically tracking movements and activities.
During a recent presentation at the Colorado Chapter of the Wildlife Society, Dr. Cassidy shared insights on what CPW’s monitoring efforts have shown about wolves in the Centennial State.
“Something people don’t realize is that wolves are among the furthest ranging terrestrial mammals in North America,” Dr. Cassidy said. “While they might not make as long of individual migratory movements as, say, a caribou, a wolf’s annual movements usually eclipse most other terrestrial mammals. This is true both for wolves in established packs and dispersing wolves.”
This means that even wolves in packs with established territories are constantly on the move. Patrolling their territory for reasons that include searching for prey, marking their territory and discouraging other wolves from encroaching.
Why is data collection so important for Colorado’s wolf program? And what are we seeing?
Due to the increased availability of GPS tracking collars, CPW is uniquely positioned to understand how wolves interact with a landscape while establishing a population.
“Our translocation protocol calls for each translocated wolf to be equipped with a GPS collar,” Dr. Cassidy said. “This gives us a much higher level of data compared to previous restoration efforts, like Yellowstone and Idaho which did not have GPS technology available, and it is showing us some interesting things.”
According to Dr. Cassidy’s research, translocated wolves traveled more than 93 miles on average in the first week after release. Over the first month post-release the average distance a wolf traveled expanded to approximately 217 miles. By the one year mark it was over 2,920 miles with an average daily travel of about eight miles.
The amount individuals moved varied widely. Some wolves moved just 16 miles from where they were released during the first week while a particularly wide ranging outlier traveled over 680 miles. There also wasn’t a clear difference in behavior among sexes as both males and females showed a variety of movements.
However all of these travel numbers are based on GPS points.
Since the collars collect GPS data points at regular time intervals (usually several hours apart), the tracking of their movements is based on measuring the direct distance between two points.
“These collars help us understand how wolves are moving, but since it doesn’t show the exact path wolves are taking we very likely underestimate the total distance traveled,” she said. “For example, if we collect a data point on the eastern end of a watershed, and the next one is collected less than a mile west of it, we don’t know for certain that the wolf was only moving around in that confined area. It’s possible it could have spent potentially hours traveling in a different direction before doubling back.”
Another interesting takeaway is that the average distance traveled by wolves over the summer months was similar whether a wolf was in a pack or not. On average, wolves in packs covered a similar total mileage to lone wolves but largely stayed within a more condensed area of their territory. This shows that even when wolves have established a geographic territory they are constantly patrolling it and covering a significant distance.
What factors are contributing to wolf movement patterns?
As wolves translocated to Colorado establish a self-sustaining population they are fulfilling a natural biological behavior that influences the movement patterns CPW is observing: Dispersal.
“Many of the wolves we tracked over the last two years were classified as dispersers of a sort because they had been removed from their original packs and were looking for other wolves in Colorado,” she said.
Another factor influencing the extent of wolf movements is the relatively continuous nature of Colorado’s geography compared to some other places where wolf reintroduction has occurred. A prime example is Isle Royale National Park, which reintroduced 19 gray wolves in the late 2010s.
“Isle Royale is an island in the middle of Lake Superior, so it has pretty established boundaries that wolves are not able to cross outside of an occasional ice bridge back to the mainland,” Dr. Cassidy said. “In Colorado we have less stark boundaries and wolves are able to travel greater distances when dispersing.”
One fascinating outlier is a female wolf who has covered more than 4,900 miles in the last year, which might be a record. According to Dr. Cassidy the closest published comparison is a wolf in Mongolia that traveled 4,536 miles in a year near the Gobi Desert. A noteworthy difference between these two wolves’ movements is the human density and development they faced.
“There’s definitely not an I-70 that goes through the Gobi Desert, so it’s pretty incredible to think about the differences between how many human-made obstacles the wolf in Mongolia faced versus the wolf that’s traveling around Colorado,” she said.
Imagining this far-ranging Colorado wolf’s traveling distance as a straight line highlights just how far it has traveled since being released. Were this wolf to have traveled in a straight line, it could have made the trip from Denver to San Jose, Costa Rica, and back with more than 180 miles to spare.
“Some of these movements are incredibly impressive, but hopefully these wolves are not moving around forever because we want them to pair, we want them to settle into a territory and reproduce,” Dr. Cassidy said.
Beyond the biology: why pack formation is crucial
Pack formation is tied to successful breeding which makes it a crucial part of Colorado’s wolf restoration effort. Pack formation also carries a number of benefits for both wolves and producers.
Across western North America, average wolf life expectancy is much, much lower than many anticipate. Although some gray wolves live to be over 10 years old, the average life expectancy is roughly 3 years.
This is because life as a wolf is dangerous.
From human-caused mortalities (both legal and illegal) to natural ones, there are many hazards to wolf survival. Territorial disputes with other wolves, disease and starvation, not to mention fatal injuries from large prey or other predators, are common causes of death in wolves. This is especially true for wolves who are not part of an established pack (i.e., dispersers).
“Dispersers often have lower survival than territorial wolves, so as managers we’re definitely paying attention when wolves are meeting and pairing,” Dr. Cassidy said. “Pack inclusion has been linked to increased hunting success, increased pup survival, and just general increased survival against all mortality types for adult wolves.”
The benefits of pack formation, from a species management perspective, go beyond the biological implications.
“When a wolf is patrolling a territory, that’s a much smaller area it is traveling than if it was wandering around and looking for a territory and a mate,” she said. “It becomes a little bit more patternable and identifies an area where we can expect them to be.”
This information helps CPW’s field staff prioritize where conflict minimization tools (such as fladry and scare devices) and techniques (like range riding and hazing) should be deployed to address potential wolf-livestock conflict.
Establishment of territory also informs release locations for future translocations.
“When we plan releases, we consider where established territories are and where lone wolves potentially looking for mates are traveling,” Dr. Cassidy said. “This allows us to both avoid putting a translocated wolf into an area where there might be territorial disputes and hopefully facilitate successful pairing with a prospective mate.”
Future of CPW’s wolf activity monitoring
The movement-tracking data CPW is gathering and analyzing is important, but it is not something CPW will always have access to on this level.
Currently, Colorado has a high proportion of its wolf population collared as a result of CPW’s translocation protocols.
These protocols require every wolf translocated to the state to be equipped with GPS collars that take GPS data points at set intervals. Once a packet of data points are taken by a collar they are transmitted via satellite. This process usually takes between 16 to 24 hours but can be delayed by a number of factors such as dense cloud cover and closed terrain.
This information allows CPW staff to know where wolves have been but not where they currently are.
As wolves naturally reproduce the total percentage of collared wolves will decrease, but CPW will work to keep at least two collars in each established pack as part of its management efforts. Maintaining this level of collaring will allow the agency to track the territories of packs even if it can’t identify the movements of each individual wolf.
For Dr. Cassidy, one of the most interesting aspects of the upcoming summer is watching Colorado’s wolf population begin to develop more complex packs.
When packs first form, they often only consist of a breeding pair and pups born that year. This year in Colorado, packs are a bit more complex and generally consist of the breeding pair, yearlings or other related adults, and new litters of pups. This will make monitoring these packs a bit more complicated, but CPW staff are eager to take on the task.
“When a pack contains adults and pups from consecutive litters, wolves other than the parents of the current litter often act as babysitters and playmates to the young pups throughout the summer,” Dr. Cassidy said. “These behaviors offer a peek into the highly social, cooperative nature of wolves. By using a number of different methods we get a glimpse of wolves living their lives and working together to raise the next generation, which is one of the most rewarding parts of our monitoring efforts.”
Written by Luke Perkins, a Statewide Public Information Officer for Colorado Parks and Wildlife.