Courtesy of Bureau of Land Management
Blog by Erin Hauge
The days are growing cooler and there’s a velvety, quiet layer of low mist that covers the open fields and sloughs on the Preserve these mornings, foretelling the changing seasons. It was beautiful and chilly as we headed out for the camera checks on this morning.
One of our trail cameras caught the crew on a recent morning. From left to right: Elizabeth, Emma, Jim and Richard. Courtesy of Bureau of Land Management
Beautiful misty morning on the Preserve. Erin Hauge
Spider webs were covered in morning dew and glowed in the fall sunlight, waiting for unsuspecting insects to become entangled. The spiders must have to wait patiently for the dew to dissipate, making their webs once again almost undetectable to insects flying near.
Spider web with morning dew and a large orb spider warming in the sun. Erin Hauge
As we move in to fall, our crew is thinking about how the changing seasons might affect mountain lion behavior, movement and dispersal from the Sierra Nevada. As snow begins to fall on the high peaks, some lions may feel the call to explore the lower elevations, looking for available territory and deer. We know that as lions explore new landscapes looking for territory, there are some important and necessary attributes that would attract a lion to an area: Minimal human interference, having enough prey to hunt, particularly deer; and having enough vegetation cover to be able to remain safe and undetected and to use for stalking and ambush while hunting.
There are two important habitat types that contribute to setting up a suitable territory for mountain lions. The first is known as the “edge zone” which contains a combination of cover areas for lions to stalk and set up ambush that are next to open areas where they can move and bring down prey. The second is the ‘home range’ which is a defined area regularly patrolled and marked by the lion and can vary in size depending on the individual and on space availability. A territory can be defined as an area that contains all the resources necessary to live and to raise young, such as adequate prey with areas to stalk and hunt, reliable water sources and safe den sites for raising kittens. Male mountain lions need more territory than females do, and territories can vary greatly in size, generally from 10 to 370 square miles!
Example of an edge zone on the left. An area where lions have cover but also room to run. Example of home range on the right. Remote with lots of cover and possible den locations, a slough nearby and deer and other prey animals frequent the area. Erin Hauge
What we know so far about the Cosumnes River Preserve is that it may be unlikely that there’s a resident mountain lion here at this time. Lions that are sighted seem to be passing through, exploring the area to determine if it’s suitable. It is possible that a mountain lion could set up in the more remote areas of the Preserve and with the healthy deer population here, they would eat pretty well. As we mentioned in a previous post, the lower Preserve is fairly flat with a combination of grass savannahs, riparian oak forests, sloughs and dense vegetation bordering agricultural fields. In other words, there are some good ‘edge zones’ that would provide cover and open areas for taking down prey. There are also some good ‘home range’ qualities on the lower Preserve, including the essentials – prey, water and some remote areas that might provide possible denning sites.
The bug in the equation is human development and habitat loss. The Preserve is bordered by encroaching cities, highways and commercial agricultural operations that can view large predators as a direct threat to livestock and even human safety. Studies are coming to light, though, corroborating that mountain lions are fearful of humans and will avoid them at all costs. There's a great study that came out in June 2017 from the UC Santa Cruz Puma Project that documents lion feeding times when exposed to different sounds. Check out this short video of a mountain lion feeding with a control sound of a Pacific tree frog in the background and then human voices. https://www.youtube.com/watch?v=TVqOhkK8fKk&feature=youtu.be
Read about the UC Santa Cruz Puma Project study here: https://news.ucsc.edu/2017/06/puma-fear.html
And a 2016 encounter between a mountain lion and a hunter in Mono County, CA also illustrates the point. The hunter was lying under cover and in wait, using a rabbit call to draw in coyotes. He instead drew in a female mountain lion who trounced him and upon realizing he was not what she expected, quickly took off running. Unfortunately the hunter then shot and killed the mountain lion as she was running away. But clearly, the mountain lion never intended to interact with the human, she thought she was going in for a quick meal of rabbit.
In the Field: We got some great images of bobcats again this week on the cameras including – a bobcat kitten! This young one came by one of our cameras with his or her mom and even paused to check out the infrared light coming off of the camera. Something in the brush caught their interest, maybe a rabbit as this camera captures a lot of rabbit activity. They ran out of camera range and then about eight minutes later a coyote came by the camera, not on a chase but he walked off in the same direction that the bobcats had gone.
Bobcat kitten and mom! Photos Courtesy of Bureau of Land Management
Another interesting thing we saw on camera was how distinctive bobcat markings are. Every bobcat has a distinct set of markings, stripes and spots, that can be used as an identifier for each animal. These two pictures below show clearly that there can be quite a variety of marking patterns. There are even computer programs that can run pattern recognition on bobcats to be able to recognize individuals and so help get more accurate population estimates.
Two different bobcats, easily recognizable by their coat patterns. Courtesy of Bureau of Land Management
We also checked our bobcat scratching post at one of the more remote cameras and found a pretty obvious claw mark where a bobcat was either climbing up or down the post. Pretty cool!
These claw marks on a telephone pole near one of the cameras are just about bobcat size! Erin Hauge
One of our cameras is located in a low area on a road right next to a slough and so it gets a lot of moisture late at night and in the early morning hours. When we got there about 8:30am, the camera lens, infrared eye and all the light sensors were dripping moisture. When the cameras get that wet, they can take images that appear like there’s mist or fog in the area but in actuality it’s the wet camera. In addition, this camera has had firing gaps of up to two days with no images, which is a red flag as there is generally a lot of bird and deer activity at this location. It’s unlikely that no birds or animals walked by or even a branch or two waved in a breeze. So we took a second trip out into the field today and switched out the camera with one we know is working. In addition, in the next week or two, we’ll be moving this camera to a nearby location, on some good wildlife travel routes and near a road, but in a more open area which will hopefully keep the camera a bit drier. All we can do is experiment with camera locations, aiming always for best technical aspects as well as most likely mountain lion routes!
Crew member Richard changing out a possibly defective camera so we won't miss that lion! Erin Hauge
Crew member Chris found an amazing sight along the bank of the slough we were exploring - a small fish appeared to have died trying to eat a smaller fish! As we gazed at the strange sight, we surmised that what looked like a small bass had eyes that were bigger than his stomach and he tried to eat a fish that was just too big for him. The smaller fish was stuck in the bigger fish, tail extruding, and both appeared to have suffocated when the bigger fish couldn't dislodge the smaller one. We brought the two fish back to the office and Chris bravely performed an autopsy to see what had happened and it did indeed appear that the big fish had tried to eat a bigger fish than he could swallow! Very unusual but it led us to wonder how often this happens in the wild.
We found a small bass that looked like it had tried to eat another fish that was too big for it! Crew member Chris bravely brought the unfortunate pair of fish back to the office for further inspection! Erin Hauge
Finally, fall is a fabulous time for watching for wildlife tracks. We saw a great set of deer tracks showing what looks to be a typical walking gait where the hind hoof just about exactly steps into the front hoof track as the animal moves along. And we saw a set of river otter tracks as the critter moved across the muddy bank of a slough. We found some freshly eaten freshwater clams on the bank nearby so maybe this otter had recently had a feast!
The typical walking gait of a deer. Can you tell which way this deer was walking?. Erin Hauge
Tracks of a river otter in a muddy slough bank, hind paw on top left, front paw on lower left. Erin Hauge
As the heat abates and the rainy season begins, there will be tracks aplenty as the hard, dry summer substrate gives way to lots of mud and softened dirt. Will there be some large, round feline-looking tracks among the wildlife moving here? We can’t wait to find out!
Great horned owl camera fly-by! Courtesy of Bureau of Land Management
River otter nighttime escapade. Courtesy of Bureau of Land Management
Buck startling at camera's infrared flash. Note his hooves jumping and disturbing the dirt. Courtesy of Bureau of Land Management
Bobcat out during the day. Though often nighttime and dusk and dawn hunters, they can be seen at any time of day. Courtesy of Bureau of Land Management
Coyote coat colors can vary and this one has pronounced rust around his or her neck and ear areas. Courtesy of Bureau of Land Management