Identifying Denali's Wolves

sketches of six wolves identified by Adolf Murie in his book The Wolves of Mount McKinley
Figure 1. Individual wolves identified by Adolf Murie in his book, The Wolves of Mount McKinley.
Adolf Murie’s 1944 work The Wolves of Mount McKinley was a landmark study on wolf behavior, biology, and ecology. His time spent observing one pack allowed him to distinguish individual wolves (Fig. 1). By presenting wolves as individuals with specific roles within the pack, he helped erode stereotypes of wolves and was instrumental in changing wolf management policy. Subsequent researchers in Denali National Park and Preserve (Denali) have formally monitored wolf abundance, territories, and reproduction using radio-collars and aerial tracking since 1986 but reliable data on pack composition and age structure has been limited. There is a growing body of research elucidating the importance of social group composition such as breeding status, sex, age and/or size of individual wolves within a pack. Wolf pack composition can influence a pack’s hunting success, territorial defense, recruitment, and pack persistence. A Centennial Challenge Project initiated in 2016 is investigating rigorous methods for identifying pack composition, including evaluating methods for reliable identification of individual wolves in packs.
a computerized grid overlays a tiger's stripes to identify it
Figure 2. Algorithms confirm individual tigers based on stripe patterns.

Hiby, Lovell, Patil et al. 2009 photo

Methods

Visual recognition of individual wild animals remained an uncommon tool in modern peer-reviewed research until the advent of algorithms which could “prove” that the stripes of a tiger in one photo matched those in another (Fig. 2). Individual identification of wolves provides more opportunity for human error and bias, as they lack clearly defined patterns of other animals such as tigers and leopards. Previous claims of regarding the ability to identify individual wolves during aerial tracking in Denali specifically have drawn criticism.
a brown box-shaped trail camera
Figure 3. Reconyx PC900 trail camera.

Reconyx photo

As part of the Centennial Challenge project, we investigated the potential for using images captured from high-quality trail cameras (Fig. 3) deployed at den sites and winter wolf kill sites to determine pack composition for packs in Denali through identification of individual wolves. We analyzed over 11,000 photos of wolves from high-quality trail cameras deployed at den sites and winter wolf kill sites from 2013 to 2016.

Field Marks

All photos in this section are from trail cameras unless otherwise noted.
close up profiles of four wolves

NPS photos


The pattern and color of facial markings can be useful for distinguishing individuals, though to be reliable it requires high quality photos and can be subject to seasonal change.
five photos depicting wolf chests

From left to right - trailcam / NPS photo, trailcam / NPS photo, Flickr stock photo, trailcam / NPS photo, Flickr photo / Patrick Kuyper

Chest blazes and bars are particularly useful for differentiating black wolves. Gray wolves can also have distinctive chest patterns.
two images, one showing two gray wolves and a black wolf, the other showing a gray wolf

Related wolves within a pack can be quite distinctive in appearance, although this is not always the case. The photo on the left shows a young black wolf (right), a young gray wolf (middle), and a collared black wolf which is graying with age (left). What distinguishing characteristics can you detect on the wolf to the right?
three photos; one shows the angle of dark hair on a wolf's back, the second shows two wolves at a carcass, and the last shows the gradient of dark to light fur on a wolf

NPS photos


The appearance of the saddle/shoulder/back area is quite variable. On a gray wolf, the level and angle of the area of darker-tipped guard hairs on their back can vary, as can the level and angle of any lighter coloration below that before it transitions to the ventral white. These lines can also be visible on black wolves.
three wolf tails

NPS photos

The size, shape, and location of the scent gland spot on the tails of gray wolves is a consistent and readily visible mark, even in nighttime photos. The shape and extent of the dark tail tip is also helpful.
two wolves, one adult and one pup
Figure 5. Compare the adult (L) and pup (R) from the same pack in mid-November pelage.

NPS photos

Age & Sex

Literature exists on the differences in appearance and morphology of pups (<12 months) compared to adult wolves. The most helpful factors in photos are size, ruff hair, snout length, and to some extent coloration and behavior (Fig 5). In addition to the characteristics of sexual dimorphism (Fig. 6), evidence of sexual organs can sometimes be distinguished in photos and provide additional clues for determining sex of individuals.
illustrated comparison of male and female wolf
Figure 6. Differences between male and female wolves (from Yellowstone Park Science)

NPS photo

Conclusions

By combining observations of size, gender, and pelage with additional contextual information about the packs, we believe consistent individual identification is possible assuming a photoset of suitable quality. However, it is important to recognize several limitations and that these results are from the initial stages of investigation. We note several cautions when looking through photos. Specifically, individuals can change in appearance as they age and the angle of the fur and lighting can have a dramatic effect on the appearance of wolves.

Next Steps

  • We plan to continue to deploy cameras at den and winter kill sites with the goal of accumulating a set of photos for all packs in the eastern region of Denali.
  • We could use these techniques to improve our understanding of the contribution of individual wolves to wolf viewing opportunities and wolf viewing patterns.
  • These photos could provide a compelling way to educate visitors about wolves and show the beauty and variety of Denali’s fauna.
four close ups of wolf heads

NPS photos

Practice

How many different wolves are pictured above? What clues did you use to help you determine your answer?