When the cost of not being punctual is very high

Humans go to great lengths to stand out. They wear bright clothes, style their hair, or choose bold accessories, all to avoid blending into the crowd. Many bird species do something similar: males often display vivid colors to attract mates and increase their chances of passing on genes. Some insects use bright warning colors to signal that they are poisonous or distasteful, deterring predators. Whatever the reason, standing out is a common strategy across the animal kingdom, including for humans.

Fig. 1. A bright julia butterfly © Steven H. Johnson

Yet certain species take the opposite approach. Blending into the background helps them survive longer, either by avoiding predators or by sneaking up on prey. This camouflage appears in many groups: mammals like snowshoe hares (Lepus americanus) and Arctic hares (Lepus arcticus), birds like nightjars, frogs like the Vietnamese mossy frog (Theloderma corticale), and insects like praying mantises.

Fig. 2. Vietnamese mossy frog with a moss like body. © H. Zell

Some animals use camouflage only at certain times or for specific purposes. Snowshoe hares, for example, change coat color with the seasons. In late autumn and winter they turn white to match snow; in spring and summer they switch back to brown. This strategy is shared by many temperate species that experience strong seasonal differences. By matching their background, they gain protection from predators (if they are prey) or improve their chances of catching prey (if they are predators). At least 21 mammal species are known to change coat color seasonally.

Fig. 3. A snowshoe hare with the 100% white coat with a complete camouflage with the background snow in Kluane, Canada. ©Charles J. Krebs & Alice J Kenney

Of these species, Snowshoe hares play a key role in the ecosystems where they live. As keystone herbivores and primary prey for many carnivores, their numbers strongly influence other species. Canada lynx (Lynx canadensis), in particular, track hare populations closely, producing the classic predator–prey cycles featured in nearly every ecology textbook. (Fig. 4). Much of what we know about these cycles comes from long-term research in Kluane, Yukon. Dr. Charles Krebs has been at the forefront of this work for decades, with important contributions from many other scientists. I was fortunate to assist in this ongoing project, thanks to my Ph.D. supervisor Dr. Madan Oli’s long-term collaboration with the Kluane team.

Fig. 4. Snowshoe hare pelt numbers is closely followd by lynx pelt numbers. This infomation was colelcted by Hudson Bay, a company that traded furs in 20th century. Courtesy: Hudson Bay Company

The seasonal molting of snowshoe hare is an important aspect of how it maintains camouflage against its predators. We assumed everything was going very well until some scientists noticed the greater occurrence of brown snowshoe hare with snowy background and vice versa (mismatched hares hereafter). Scientists knew from the very beginning that snowshoe hares used their white coat in winter and brown coat in later spring and summer to evade from their predators which made these mismatched hares a case study.

Fig. 5. A snowshoe hare with almost complete brown coat with predominantly snowy background in Kluane, Canada in 2017. ©Charles J. Krebs & Alice J Kenney

In recent years however, the timing of molting in either season seems to have changed due to rising temperature and the change in the snow duration. As expected, the mismatched hares survive at lower rates than well-camouflaged ones (7–12 % weekly survival disadvantage). Long-term studies across larger areas may refine these estimates, but the pattern is clear: when hares stand out, predators like Canada lynx and coyotes (Canis latrans) detect them more easily..

Two processes likely drive this reduced survival. First, and most obvious, predators spot mismatched hares more quickly. Second, though less certain, the hares may experience added stress from higher predation risk, prompting behavioral changes to avoid detection. Either way, the outcome is the same: lower survival.

Some species behaviorally compensate for mismatch. For example, rock ptarmigan (Lagopus muta) roll in mud or soil when snow melts early. Snowshoe hares appear to lack this flexibility; they rarely adjust their position or behavior to improve concealment when mismatched.

Recent research offers a glimmer of hope, however. In long-term studies at Kluane, Yukon, scientists have observed subtle behavioral shifts in mismatched hares, they reduce activity overlap with predators and concentrate nocturnal movements around midnight to early morning. These adjustments appear to lower interaction and may partially offset the costs of poor camouflage. However, longer term data is needed to better understand this pattern.

Climate change is the main driver behind increasing mismatch. Rising temperatures shift the timing of snow cover, while hare molting cues (day length) remain largely unchanged. Snowshoe hares are just one example; many other seasonally molting species face the same challenge. As snow patterns continue to shift, camouflage that once ensured survival may become a liability.

Bibliography

Ghimirey, Y., Kenney, A., Krebs, C.J. & Oli, M.K. 2025. Seasonal coat colour moulting phenology of Snowshoe Hares in a Yukon boreal forest undergoing climate change. Royal Society Open Science. 12: 250662.

Krebs, C. J., Boonstra, R., Kenney, A. J., & Scott Gilbert, B. (2018). Hares and small rodent cycles: A 45-year Perspective on Predator-prey Dynamics in the Yukon Boreal Forest. Australian Zoologist, 39(4), 724–732.

Krebs, C. J., Boutin, S. & Boonstra, R. (2001). Ecosystem Dynamics of Boreal Forests: The Kluane Project. Oxford University Press.

Mills, L. S., Zimova, M., Oyler, J., Running, S., Abatzoglou, J. T., & Lukacs, P. M. (2013). Camouflage mismatch in seasonal coat color due to decreased snow duration. Proceedings of the National Academy of Sciences of the United States of America, 110(18), 7360–7365.

Oli, M. K., Kenney, A. J., Boonstra, R., Boutin, S., Murray, D. L., Peers, M. J. L., Gilbert, B. S., Jung, T. S., Chaudhary, V., Hines, J. E., & Krebs, C. J. (2023). Does coat colour influence survival? A test in a cyclic population of snowshoe hares. Proceedings of the Royal Society B: Biological Sciences, 290(1996), 20221421. https://doi.org/10.1098/rspb.2022.1421

Peltier, T. R., Shiratsuru, S., Zuckerberg, B., Romanski, M., Potvin, L., Edwards, A., Gilbert, J. H., Aldred, T. R., Dassow, A., & Pauli, J. N. (2023). Phenotypic variation in the molt characteristics of a seasonal coat color-changing species reveals limited resilience to climate change. Oecologia, 202(1), 69–82.

Wilson, E. C., Shipley, A. A., Zuckerberg, B., Peery, M. Z., & Pauli, J. N. (2019). An experimental translocation identifies habitat features that buffer camouflage mismatch in snowshoe hares. Conservation Letters, 12(2), 1–8.

Zimova, M., Sirén, A. P. K., Nowak, J. J., Bryan, A. M., Ivan, J. S., Morelli, T. L., Suhrer, S. L., Whittington, J., & Mills, L. S. (2020). Local climate determines vulnerability to camouflage mismatch in snowshoe hares. Global Ecology and Biogeography, 29(3), 503–515.