Field Report 7: (Too) Hot and Dry Summer - What does this mean for High Desert Beavers?
Boy is it hot out there! According to the National Oceanic and Atmospheric Administration, June 2021 was the hottest June ever on record. At this point, in mid-July, our daytime temperatures continue to be above average.
We're reporting on a spring-fed tributary to the Crooked River - "Tributary B". Monitoring takes place within a spring fed stream at a working ranch, where the landowners have been stewarding the landscape, diligent over the years about planting willows to help recovery, while keeping cows out of sensitive riparian areas.
In this field report we bring you our observations and the ongoing story of the beavers in this system.
Most weekends we’ve been checking on our monitoring cameras. Initially, we'd visit the site in the afternoons, but switched to early morning visits as the weather warms and heat becomes progress. With each visit we notice the water level is dropping and dropping pretty significantly. In a matter of 6 weeks of site monitoring, we’ve seen the water drop about 2 foot total in water levels.
Normally the flow of this tributary does slow down in the summer months. We don’t have data from past seasons to make comparisons, but what we do know is that the Crooked River is flowing at a rate of about one cubic foot per second (which equates to about 7.5 gallons), which is extremely low flow.
During the past few years of monitoring beaver sites in the Deschutes River Basin and comparing notes with knowledgeable experts, it is apparent that there are noticeable and concerning impacts to riverine wildlife from this year’s drought. Beavers generally need a minimum of 2 ½ feet of water depth in order to sufficiently cover the entrance or access opening into their den. When water levels drop, predators can access the den and prey on the vulnerable beaver kits (see illustration below and the two photos of ‘Site 1’).
We documented a beaver family, consisting of two adults and two kits via videocam at this site in early June 2021. You can see a bit of their activity at this Youtube video here. In early June 2021, the beaver family vacated its den, we presume out of necessity, as the area was lacking food and water levels were dropping precipitously.
During our months of observation, we were noticing that the beavers had pretty much eaten all their food supplies within their immediate home range (close to their den and major damming activities). With a lack of nearby food, they were being forced to travel further on land to food. When beavers are forced to spend more time away from their immediate home range (and in particular more time on land), it makes them more vulnerable to predation. While some areas of the stream are still relatively deep, many areas are now lower than one foot in depth and each time we go out to the site, there are fewer deep spots for the beavers. Less water availability means the beavers are more vulnerable to predation.
Beavers have definite preferences for particular food sources (willow, poplar, alder). During our most recent visit to the site, we noticed that there was evidence of beaver chew on their less preferred food (i.e., golden current). As the water level drops and dries up, the beaver’s food sources are drying up. They are traveling further and seeking out alternative food sources.
We have been monitoring with multiple cameras at multiple sites and see that beavers make appearances for some days and then they are off to different places. As we have been reviewing the video footage from different dates, we believe that the family unit has left the den. We have evidence that by necessity the beaver family traveled 200 feet on land in order to reach more available food and water sources in a human-built pond of an adjacent stream.