Durango recorded above-average temperatures this winter, with record highs in December and February and much of January temperatures in the high 40s and low 50s, according to National Weather Service data.
For wildlife, an unusually warm and dry season can have far-reaching impacts.
Jamin Grigg, a senior wildlife biologist for Colorado Parks and Wildlife’s southwest region, said this season ranks among the worst winter conditions he has seen his more than 20-year career.
“Weather-wise, I would say this is the most severe non-winter – just total non-winter – that I’ve ever observed, both in terms of warm temperatures and lack of snowpack,” he said.
Grigg said CPW has already observed some impacts.
Bears are emerging from hibernation early, deer and elk are migrating sooner, and shrubs and trees are budding early – which increases the risk of a late freeze damaging plant growth.
Low snowpack and drought have reduced forage conditions across the landscape, he said.
Durango has seen several extended dry periods since December, National Weather Service Meteorologist Gillian Felton told the Herald.
Those dry spells include a 22‑day stretch from Dec. 4 to 25, 13 days from Jan. 10 to 22, 19 days from Jan. 24 to Feb. 19 and another period from Feb. 21 to April 1.
Low precipitation and extended drought can reduce habitat carrying capacity – the number of animals an area can support – for species like deer, bears and elk, Grigg said. A lack of moisture can leave wildlife – especially juveniles – in poor physical condition, making them more vulnerable and reducing survival rates, he said.
Persistent drought can deplete soil moisture and forage, which can lead to multiyear impacts on animals’ body condition, habitat quality and population health.
Reduced plant life means less food for bears and other animals, forcing them into smaller areas with better soil moisture and vegetation. That, in turn, increases competition and predation risk, Grigg said.
Drought years can also increase human-wildlife conflicts, he said. Residents should be prepared as Durango enters its spring and summer months.
“If we stay in this warmer system through the summer, what we’re going to see is a lot of wildlife populations that are going to be stressed for natural food availability,” he said. “So I would … urge residents to potentially anticipate a higher‑than‑average number of bears in and around town – in and around residential areas – bears that are stressed and looking for human food sources.”
Deer and elk are also more likely to congregate on private lands and pastures if forage in the wild remains poor through the summer, he said.
Durango and surrounding areas have a fairly high density of mountain lions, Grigg said, and if deer move closer to town, mountain lions are likely to follow, because deer are a primary food source.
CPW has not yet seen increased predation on pets or livestock, but officials are monitoring the situation, he said.
CPW aquatic biologist Kade Jackson said he hadn’t observed any major impacts on aquatic wildlife in the Animas River as of March, but flows and temperatures are being monitored daily.
“What we’re still anticipating is a less-than-great spring runoff,” he said.
Weaker spring runoff can leave stream gravels uncleansed, Jackson said, which can harm spawning habitat for trout and other native fish and reduce survival of eggs in the gravel.
Water temperatures may rise earlier than normal, Jackson said, and combined with low flows, can stress fish – especially trout and Kokanee.
Lower water levels and higher temperatures associated with drought can reduce available habitat for Kokanee and cause an oxythermal squeeze – when warm surface temperatures and depleted oxygen levels compress the thermocline – which can increase stress, predation and competition for food.
“We don’t quite see this in (Lake) Nighthorse, but McPhee and Vallecito (reservoirs) it is a concern,” he said.
Voluntary noon-to-midnight fishing closures on Sundays may be implemented earlier than usual this season to reduce stress on fish, he said.
Anglers may want to seek higher-elevation streams and high-mountain lakes this summer for their fishing, which are often less impacted by warm-water conditions, or choose to visit nearby reservoirs that support warm-water and non-native species like smallmouth bass, northern pike, largemouth bass and bluegill, he said.
Durango Fire Protection District Chief Randy Black said in February the upcoming wildfire season is expected to be especially severe, which Grigg said could impact local wildlife.
While wildfires can have beneficial impacts, such as improving soil nutrients and increasing forage production after recovery, they can also negatively affect wildlife, he said.
Large wildfires can reduce forage and habitat, increase sediment runoff, lead to landslides and mudslides, and cause other hazards that stress wildlife and reduce survivability, he said.
CPW is taking a “wait and see” approach to spring and summer precipitation, Grigg said. But there’s an expectation that warm and dry winter weather could become a new norm.
“Based on what all of the climate models are predicting and have been predicting for decades, we’re expecting this to become more of a normal pattern, which is pretty concerning on different levels,” he said.
Prolonged dry and warm winters can change spring runoff, reservoir levels and habitat quality.
Grigg said CPW will likely have to focus more on managing reduced habitat capacity and dealing with human-to-animal and animal-to-animal conflicts.
It can take several years to recover from seasons like this one, Grigg said – even if following winters are colder and wetter.
“What most people don’t totally understand is the longer-term impacts that these drought years have in terms of soil moisture and forage conditions (and) production, potentially for a number of years to come,” he said. “It impacts body condition and overall health of animals as they head into next winter.”
epond@durangoherald.com
