River Rising – Oh, and Bobcat Kittens!
The Cosumnes River is rising again! It’s that time of year when the rains start filling the rivers and we sure saw that today. Just the small amount of rain we’ve had in the last few days had us nervous about reaching our farthest camera, which is located in an old oak forest across the Cosumnes River and a large flood plain. We weren’t sure what we’d see as we made this camera our first stop in the morning with the intention of pulling it completely and moving it back to the south side of the river.
We weren’t disappointed as we came up to the low-flow dam where we cross the river! Where the river bed had been dry and sandy, full of coyote tracks and good walking just several weeks ago, there was now running water, not too deep yet but flowing along and covering the riverbed nearly from bank to bank.
We breathed a sigh of relief to know we’d reached this camera in time but none too soon. With more rain predicted this week, only a few more inches of water will have the low-flow dam immersed and unpassable probably for the entire winter now. Staying ahead of rising water, impassable roads and flooding will now be our calling as we work to keep the cameras deployed, but safe and reachable. These trail cameras are water resistant but not water-proof, so if they become submerged in floodwater, they’ll stop working.
We also practice safety out in the field – the number one priority above all else is to keep the crew safe. While it might seem reasonable to wade across the dam in a few inches of water in rubber boots this should never be attempted. The power of water can be deceptive. Not only can the current running even a few inches deep in a river like this be quite strong, the dam itself could be slippery making a fall into the flowing water become more much likely. As we watched the strength of the current of water moving through the box culvert that directs water under the low-flow dam, it was clear that once water immerses the dam itself, passage will be too risky and stopped for the season. Luckily, our cameras on on the same side of the river as we are now!
Once the low-flow dam is covered in water, this corridor will be unavailable to animals during the winter and they’ll have to find other ways to cross the river. Rivers are natural barriers that can influence animal populations and their genetic diversity. We’ll be watching to see how animal movement changes with the rising of the Cosumnes River.
In the Field:
The camera we removed from the north side of the river was placed on a big oak tree that overlooks many wildlife trails that look to be currently in use along a grassy levee overlooking the river. The camera is near another one we have in place right along the road where a mountain lion was spotted earlier this year so we know lions use this corridor. We’ve also seen deer, their scat and tracks and even bones in this area in addition to bobcats and coyotes. We cleared the low vegetation as much as we could to prevent camera triggers by weeds and branches blowing in the breeze but we’ll have loppers with us next week in case we get an image overload on the camera! When we get thousands of images on any camera we immediately suspect wayward vegetation and wind or lots of human activity. We’ll be looking forward to seeing what we’ve caught on this camera next week!
Mountain lion 411!
Last week’s coyote and skunk encounter got us thinking about how mountain lions might interact with the skunks we have on the Preserve. Intuitively, we’d think that a skunk would be easy prey for an ambushing lion. Upon some investigation, though, we learned a thing or two!
A behavior called ‘encounter competition’ can occur between the same species or between two different species and involves gaining access to important resources like food or mates. A study published in The Canadian Field-Naturalist documents a food encounter competition between a Western spotted skunk and a Mountain lion and if you think the lion won, keep reading! (We have Striped skunks here on the Preserve but no Western spotted skunks that we’ve seen.)
A game camera was placed on a black-tailed deer kill and recorded the interaction between a Mountain lion who would come to feed on the carcass and a skunk who kept showing up and chasing her off! There’s a fascinating 8-minute YouTube video, link below, that shows the succession of encounters and you’ll see the skunk relies on aggressive posturing and tail lifting, which definitely set the lion back. The study found evidence that potential predators, like lions (and we would surmise probably coyotes too), actually learn from experience to identify the aposematic coloration of skunks with something not worth messing with.
Aposematic coloration is a defensive tactic that some species evolve that uses distinctive colors and patterns to warn potential predators that the species may taste bad, be poisonous or, in this case, smell very, very bad! So all the skunk had to do was look tough and the lion may have associated that black and white coloring with trouble.
Watch the encounter competition between a Mountain lion and Western spotted skunk here! https://www.youtube.com/watch?v=bfm-7WwUCCg
A highlight of our camera check day came when we were examining camera images and came across – bobcat kittens! A mom and two kittens strolled by the camera in the afternoon last week and it was easy to see the kittens are plump and healthy as they follow mom past the camera!
Bobcats can produce litters primarily in February and March but as we see by these photos, they can breed at any time of year if resources are abundant and the seasons aren’t too harsh. It makes sense that more kittens are produced when prey is plentiful and habitat is available. When a female bobcat comes into heat, she makes it known through vocalizations, behavior and scent dispersal. A male and female bobcat may come together, court and mate repeatedly over a period of several days and when they separate, the male moves on and does not help with rearing the kittens.
Bobcats usually have one litter per season with 2 to 4 kittens. There’s about a two-month gestation period so many kittens can be born between April and June. Kittens are born in well-hidden natal dens and the moms usually secure several other safe den sites, called maternal dens, that can be used to move the kittens around to avoid predators and other threats.
Bobcat kittens generally remain exclusively in the natal den for the first 4 to 6 weeks of life, so these little ones following their mom around may be two months old or a bit older.
Bobcats would likely be competing with coyotes on the Preserve for territory and food. Both prey on rodents and rabbits and even deer. Their hunting styles are different as bobcats are generally ambush predators, surprising prey by pouncing, while coyotes are generally coursing predators who run down their prey. Mountain lions and free-roaming dogs are also deadly threats to bobcats. Humans are probably the biggest threat because of habitat loss due to development and predator intolerance.
Coyotes sometimes kill bobcats so these kittens will need protection until they grow much bigger. It’s understood that bobcats may strive to minimize contact with coyotes by being more active during the daytime, so these young ones may be safer out during the day then being with mom on a nocturnal outing.
In 2013, the Bobcat Protection Act was passed, which makes it illegal to trap bobcats in California. There are still hunting seasons for bobcat, however, and poaching is always a direct threat.
Meet the Crew!
Our amazing crew is out in the field working rain or shine and we thought you’d like to meet them!
Meet Mary DuBose, long-time Cosumnes River Preserve Volunteer Naturalist, Environmental Educator and Citizen Scientist
“I like so many aspects of being on the Mountain Lion Crew that it’s hard to isolate just one. I like being out early in the morning, when the wildlife are more abundant than later in the day, and you just might catch a coyote, a deer, or an otter family by surprise, doing what they do. I like being able to go to places on the Preserve that I don’t usually go. I like reviewing the wildlife photos at the Visitor Center—it’s kind of like being a fly on the wall (or on the tree or post, in this case) and getting to see the activity of the Preserve’s mammals—none of which have been mountain lions yet, but it’s fun seeing what the rest of the wildlife are up to. And, last but not least, I like working with kindred spirits, fellow team members who also appreciate the beauty of the Preserve and the privilege of being part of an important citizen science project.”
Aerial Photo Features!
It’s time for more aerial views of our lion cams! Viewing these images, it’s important to think ahead and imagine how these landscapes will change with winter precipitation and possible flood events. We’ve already moved one camera in anticipation of wetter weather and we’ll see what the coming months bring! Thank you, Tom!
Critter Camera Captures
Behavior of North American Mammals, Peterson Reference Guide by Mark Elbroch and Kurt Rinehart
Encounter Competition between a Cougar, Puma concolor, and a Western Spotted skunk, Spilogale gracilis: http://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/1410