Winter is here! This means that my favorite eastern fox squirrels 🐿are facing the biggest problem tree squirrels face all year- food shortage. In many places it is raining 🌧, snowing ❄️, or just plain freezing ☃️outside. These are not ideal conditions for trees 🌲to be producing nuts and seeds 🌰. Most tree squirrels do not hibernate and have to feed themselves throughout the winter when there is very little food in the natural environment.
Not to worry! Squirrels have been preparing to face this challenge all year long! 🐿🏋️♀️In the fall when nuts and seeds are most abundant in the environment squirrels are hard at work creating large hoards of food. It is estimated that eastern fox squirrels can store up between 3,000 and 10,000 nuts per season! Squirrels then rely on the food they stored in the fall to survive the winter 🐿❄️🌰.
The food squirrels store is so valuable to them in the winter they do not want to just bury any nut. Squirrels want to ensure they stash away only the best nuts! 🏆🌰To do this eastern fox squirrels have worked out a two-step nut evaluation processes.
Step One: Paw Manipulation
When a squirrel comes across an a nut still in the shell the first thing they may do when considering whether or not to store it way for later is a ‘paw manipulation’ or ‘paw maneuver’. The squirrel will rotate the nut in its front paws several times.🌰🐾
Rotating the nut between their paws allows them to feel for any cracks or blemishes in the shell. A damaged shell may mean that the item is infested by a bug 🐜 or will rot 🤢quickly once placed underground and therefore not be edible by the time winter rolls around.
Handling the food in this way also helps the squirrel either prepare to place the nut in its mouth to carry out step two of the assessment process, the head flick, or to begin eating the item.
Step Two: The Head Flick
The final test the nut has to pass before being stored is the head flick. Once the squirrel has used the paw manipulation maneuver to situate the food in its mouth it will then perform a quick jerking motion with its head. This causes the nut inside the shell to move and bounce off the inner walls of the shell.
By flicking its head and causing the nut inside the shell to move the squirrel is able to double check that there is actually something inside the shell and to get a rough estimate of the item’s weight. ⚖️🥜
The head flick is extremely helpful when it comes to making sure only the best quality food is being stored for the winter. 🌰🏆❄️After all the work it takes to bury a nut for the future it would be a major bummer if it turned out there was no actual food inside the shell or only a really tiny morsel!
Watch These Assessment Behaviors in Action!
(Preston & Jacobs, 2009)
This week's squirrel spotlight star ⭐️🐿 is the Grizzled Giant Squirrel (Ratufa macroura). These oversized tree squirrels 🌲are native to India and are sometimes called the Sri Lankan giant squirrel. India is known to have three giant squirrel species; the black giant squirrel, the Indian giant flying squirrel and the grizzled giant squirrel. The grizzled giant is the smallest of the bunch.
Grizzled giant squirrels spend their entire lives in the tree tops 🌲 only appearing on the ground occasionally to escape predators. This species lives a solitary lifestyle and will live most of their lives alone with the exception of mating and caring for young.
Unlike most of the tree squirrels we are familiar with in North America, the grizzled giant is extremely territorial. When an intruding squirrel enters another grizzled giant's territory they will be met with an extremely loud vocalization 📣by the territory owner. This serves as a warning to leave the area before being chased out!
Grizzled giant squirrels are struggling in the wild. Their population has been declining at a steady pace over the last 30 years due primarily to habitat loss caused by farming, logging, and human settlement.
The grizzled giant squirrel is listed as near threatened on the IUCN Red List. The Red List is assembled by the the International Union for Conservation of Nature (IUCN) and serves as a guide for indicating a species well-being in the wild and as a barometer of how close they are to becoming extinct. The Red List is a very commonly used tool in the creation of conservation and species management plans.
Species are assessed and given a category on a list that ranges from "Least Concern" to "Extinct." For example, the chart below shows how the grizzled giant squirrel faired in its IUCN assessment.
Grizzled giants are considered Near Threatened. In comparison to endangered species such as the Asian elephant (Elephas maximus) or critically endangered species like the Sunda Pangolin (Manis javanica), grizzled giants are doing pretty well. However, it is important to take their Near Threatened listing seriously. Work done now to stop further population decline could prevent this species from becoming endangered in the future.
Currently, populations of grizzled giants are being closely monitored. Many live within protected lands free from the threat. Further, trade of this species is highly regulated.
Check out this adorable video of a Grizzled Giant Squirrel enjoy a snack!
(Nowak, 1991), (Joshua & Johnsingh, 1994), (Molur et al. 2005), (IUCN Red List (December 2018))
Tomorrow Wednesday November 14th the Public Broadcasting Service (PBS) will be airing "A Squirrel's Guide to Success" 🐿🏆. This rivetingly adorable documentary follows an orphan baby red squirrel as it grows up and learns how to be wild 🌲🍂. Along the way they highlight the amazing super powers of squirrels by interviewing expert squirrel gazers 🐿👀about their ground breaking science 🔬.
Three of my all time favoriate squirrel gazers and mentors are featured! In this post I am going to talk a-little bit about the part each these three amazing squirrels scientists 🐿🔬play in this new documentary.
BUT first it is important to address that the real stars ⭐️ of this show are the UC Berkeley campus fox squirrels! I think they enjoyed filming and quickly embraced the camera crew and all their gear 🎥📸!
I was not interviewed for this particular show, but I did serve as the on set squirrel trainer 🐿🏋🏻♀️! My job was to assist the squirrels in their on camera appearances 🎥🐿and show off their amazing ability to leap on to tiny branches with grace. To do this I trained fox squirrels on the Berkeley campus to leap across obstacles on a large magnetic wall. The back of my head also makes a very brief appearance in the film 😂.
During my time as an undergraduate at Berkeley 🎓I had the opportunity to work with three veteran squirrel gazers 🐿👀. Each of them are not only meticulous animal scientists but amazing mentors and teachers who fostered my love ❤️ for science 🔬 and squirrels 🐿.
Dr. Mikel Delgado, Dr. Lucia Jacobs, and Dr. Robert Full are each featured in this new documentary describing how their work sheds light on the awesome traits that make squirrels such a successful species.
Dr. Mikel Delgado is a super star ⭐️scientist and squirrel gazer 🐿👀. Without her I would not be where I am today. She patiently took the time to show me the ropes when it came to working with wild squirrels and surviving in academia. In A Squirrel's Guide to Success, she explains how squirrels assess food items before they choose to store them and talks about her amazing research looking at where squirrels burry their nuts and which stored items get stolen! If you are interested in her work check out her website! catsandsquirrels.com/
Dr. Lucia Jacobs is a professor in the Psychology Department at UC Berkeley. Dr. Jacobs' research focuses on how species cognitive abilities evolved to be adaptive in the environments in which they live. I had the privilege to conduct research in her lab for 2 years, she taught me everything I know about being a squirrel scientist. In A Squirrel's Guide to Success, she explains how a fox squirrel's brain 🧠 grows larger during the season when they store food in order to help them remember where they put their nuts! 🌰🥜Check out her website for more information about all the awesome science going on in her lab! jacobs.berkeley.edu/
Dr. Robert Full is a professor of Integrative Biology at UC Berkeley. Dr. Full is an unconventional squirrel gazer 🐿👀. His research is focused on biomechanics, which is the study of the movement and structure of living organisms. In his lab researchers study the way animals move and build robots 🤖 that mimic their movements in order to contribute to technologies that could help humans. One of his projects in collaboration with Dr. Lucia Jacobs explores how squirrels use their nibble bodies and rotating ankles to traverse and jump across branches.
During my time in the Jacobs lab I trained squirrels leap onto obstacles using a magnetic wall built in the Full Lab. For his part in the documentary Dr. Full explains just how amazing squirrels are at climbing, balancing, and leaping though the trees! 🐿🌲You can learn more about Dr. Full's work at his lab website: polypedal.berkeley.edu/
The documentary is scheduled premiere on PBS, Wednesday November 14th at 8 pm PST. To look at your local listings click here to visit the PBS website.
Here is a sneak peak of the show! 🐿⭐️👀
Squirrel gazing 🐿👀on a remote field site like the James Reserve where my work is done 🌲🌻you come across a lot more wildlife than just squirrels! Having the opportunity to watch and sometimes interact with other animals on the reserve has been one of my favorite things about my time in the field.
Over the summer we came across birds, snakes, bears, and coyotes! 🐦🐍🐻🐶This post is focused on the incredible non-squirrel critters we had a chance to observe this summer. Here I discuss how they influenced our squirrel gazing and share some amazing up close bear and coyote footage caught by the reserve cameras!!! 🐻🎥🌟
At the James Reserve there is an incredible diversity and abundance of birds. We often joke that an alarm clock is not needed when staying at the field station because the hawks, Stellar's jays, and myriad of song birds will let you know when the sun is up. 🐦☀️⏰
The squirrel gazing team 👀🐿 was especially popular amongst birds while we were training squirrels to use our automated feeder. During the learning phase of our experiments we filled the tunnels of the feeder full of sunflower seeds 🌻. This is often called 'free baiting' and is done to habituate squirrels to seeing the feeder as a food source.
Free baiting the feeder in this way drew a huge crowd of both squirrels and birds! Here is a male Black-headed Grosbeak (Pheucticus melanocephalus) enjoying a free snack.
Southern Pacific Rattle Snakes (Crotalus oreganus helleri) 🐍 are a common resident of the James Reserve, one even lives right under the lodge!
California ground squirrels are a favorite snack 🐿🍴 of these snakes, so we would often run into these sneaky dudes while trapping squirrels. 'Biggie' and 'Chip' are two Southern Pacific Rattle Snakes that live under a large rock structure right near one of our squirrel colonies. We had to be especially careful to give them their space while working in that colony as the rattle snakes in these mountains in particular have neurotoxic venom that make their bites one of the most dangerous in the world!
Historically, bears 🐻have been a relatively rare occurrence in the San Jacinto Mountains. They made a notable appearance at the James Reserve last year when they tore the screen off an open window, proceeded into the lodge where they made a mess of the kitchen by opening a bag of sugar, all while researchers were sound asleep on the second floor 😴.
This year, the two resident black bears (Ursus americanus) 🐻🐻have made there return to the James Reserve. They can be seen almost nightly following a singular path around the lodge checking the storage sheds and bird feeders for food.
Here is some video footage of the bears caught by the reserve's night vision cameras! 🐻🌙🎥
Coyotes (Canis latrans) are a common site and sound on the mountain. They are often referred to as 'song dogs' 🎶🐶because of the intense call and response howling noises they make to one another during the night. This is thought to be a way to maintain family groups.
During my last trip to the Reserve I was staying in a tent ⛺️, around 10pm 🌙🌟, I began hearing coyotes howl in the distance and then all the sudden a howling response came from right outside my tent! It was an incredible experience to be so close to these beautiful animals.
Here is a video of two coyotes sent marking the dumpster area of Lake Fulmor right outside the the James Reserve!
Thank you to Dan Cooper for your gracious bird ID and Andrea Campanella Assistant Director of the James Reserve for sharing these amazing wildlife videos.
This week's squirrel spotlight star 🐿🌟is the eastern fox squirrel! This happens to be my personal favorite squirrel species. I am probably bias because I have spent most of my time as a squirrel gazing student 🐿👀🎓 working with this clever urban dwelling species.
I could talk for days about eastern fox squirrels! So, to keep myself on track I have narrowed down what I think are the top 5 coolest facts about fox squirrels*.
* Some of these facts apply to other squirrel species as well!
Top 5 coolest facts about fox squirrels 😎🐿
1.) Their brains grow to help them remember where they store their nuts! During the time of year fox squirrels need to focus on storing food for the winter they experience neurogenesis (growth of new brain cells called neurons) in the part of the brain involved with memory, the hippocampus. This is thought to assist them in remembering where they stash all their food!
2.) Fox squirrels ankles can turn 180 degrees! This allows them to quickly climb down trees 🌲head first!
3.) Fox squirrels use their heads to weigh nuts still inside their shell! 🌰Referred to by Squirrel Gazers as a "head flick," a squirrel will place an unshelled nut in her mouth and quickly shake her head. This allows her to use momentum to ensure there is something inside the shell worth burying and estimate its weight.
4.) They help plant trees! 🌲The acorns they bury and forget to dig up can grow up to become trees.
5.) Fox squirrels survive in urban environments 🐿🚎🏙. Humans are invading most of the natural land left on earth. Most of the time when humans move into an area animals move out or struggle to survive. Aside from having to avoid traffic 🐿🙅🏻🚗, fox squirrels have made themselves at home among us. These urban tree dwelling cuties may have a lot to teach us about the types of traits that make animals successful living amongst humans.
(Jacobs L.F. , 1996); (Preston & Jacobs, 2009)
The Squirrel Gazer research project 🐿👀🔎 was on the news over the weekend!
We were highlighted on STEAM Sunday 🔬, a weekly news segment that highlights scientists who do unusual things with their STEM educations. Who knew building a squirrel feeding robot 🤖was so unusual? 💁🏻🌰🐿
The goal of the STEAM Sunday segments are to expose a wide audience to all the cool careers that can result from an education grounded in Science, Technology, Engineering, Art, and Math (STEAM) and inspire a new generation of young scientists.
Aside from how cool and surreal it was to see all my squirrel friends 🐿💕😊on the silver screen 🌟, I think my favorite part of this entire experience was the opportunity to serve as an example of how possible it is for anyone to become a scientist.
I struggled in math and science throughout high school. When I graduated I did not have the grades to study science at the university level. I spent 5 years in community college working my way up from 7th grade level math.
You do not have to be a natural at something to be successful in a field. With a lot of dedication and help from others you can build yourself a foundation of knowledge upon which you can springboard yourself to the scientific career of your choice!
And hey! In the end all that time and effort was worth it! Did I mention I spend all day with squirrels now? 🐿
STEAM Sunday: Squirrel Gazer Full Video Below:
It may have taken humans a long time to discover the benefits of reusable grocery bags, but California ground squirrels have known them for a long time. Cheek pouches are the ultimate reusable bag conveniently and permanently attached to a ground squirrel's body and a lot of other mammal species for that matter (fun fact: platypuses have cheek pouches!).
Cheek pouches allow these squirrels to collect more food while foraging than would be possible to eat or carry at one time. Without the limitation of only being able to carry what could fit in their mouths, ground squirrels can load up on food and take it to a safe location to eat or store.
There is a common misunderstanding that animals with cheek pouches are storing their bounty inside their mouths. In fact, a cheek pouch is a pocket like skin tube located between the cheek and the jaw. The opening of the pouch begins at the mouth and can sometimes almost span the length of an animals entire body!
Specialized muscles help the animals empty their cheek pouches when they are ready to relocate their newly collected food. If you have a few hours to fall down a YouTube rabbit hole, I defiantly suggest watching videos of and animals emptying their cheek pouches. It is so cool!
Last week at the James Reserve I set out to find California ground squirrels' favorite food 🌰🌻🍕. Understanding what types of nuts and seeds they prefer will help me decide what to use in my automated feeder when my decision making experiment begins 🔎.
To do this I placed out a tray of 5 different nuts and seed choices and counted which the squirrels took the most. To learn more about the food preference test I use, take a look at my blog post from August.
When running these tests I set up motion sensing cameras 🎥 around the tray to ensure it is in fact squirrels taking the food. This led to an up close and personal view of California ground squirrels filling their cheek pouches with goodies! Be sure to check out the slow motion footage below!
A top priority for many tree squirrels 🌲🐿like this Eastern grey squirrel (Sciurus carolinensis) is the storing of thousands of nuts during the spring and summer, in order to survive through the winter.
Eastern grey squirrels, like many other of their arboreal relatives 🌲🌳, are scatter-hoarders. This means that they hide each nut 🌰 they find in a different location as opposed to storing all the food in a single place like a burrow.
Storing each food item in a separate location presents some serious security concerns 👮🚓. Thievery is rampant in the squirrel world! Bury a nut and a sneaky fluffy tailed intruder may come in and take it while you are away 👀🌰🐿.
Scatter-hoarders cannot defend each of their individually stored items from theft. So, instead they have developed unique anti-theft strategies to keep their hoard safe.
1.) The Take and Travel- One way to cut down on the risk your buried nut will be stolen, also referred to as pilfered, is to take your food item and travel ✈️🚗🚀as far as possible from the place you found it prior to burrying it underground.
Why? The mainstay of an arboreal squirrel's diet are tree nuts which are primarily found at the bottom of trees. So the logic follows; if there is one nut at the bottom of a tree 🌰🌲, there is likely more nuts there 🌰🌰🌰, and nuts attract squirrels 🐿💕🌰. So, if you burry your nuts around where you found it there will be more squirrels in that area that may find your hidden stash and take it for themselves! 🐿🐿🐿
2.) The Risky Run- For the braver squirrels out there another anti-theft strategy is to store your items in dangerous locations 😼🐍. For example, take your nut to a backyard that is known to have a few pesky dogs roaming around in it 🐶🐶.
Why? If you store your food in an area that few squirrels are courageous enough to search your chances of being able to pull up that nut 🌰a few months from now is greatly increased. The downside to this strategy is that you may have to put yourself in harms way to burry your food in risky locations.
I once saw a squirrel run across a busy street and burry a nut inside a small planter right outside the door to a busy Starbucks ☕️. More than likely that nut will not be stolen, but he will have to avoid traffic 🚗🚕🚙to get back to it in the future!
3.) The Fake-out- Lastly, if you find the perfect location to burry your newly found nut 🌟🌰, but you notice another squirrel is watching you 🐿👀you can always opt for the fake-out, also known as 'false caching'.
When a squirrel notices other squirrels 🐿or even sometimes birds 🐦 or humans 😳watching them bury food, they will pretend to bury it and secretly carry the item to a different storage location! When utilizing the fake-out strategy squirrels will go through the entire nut burying process, even taking the time to camouflage the fake cache with leaves 🍁and sticks just like they would if they were storing a real food item.
Why? If you are being followed by a thief, pretending to bury a food item may distract them allowing you to carry your nut to a more discrete location. While they hurry over to steal your new cache you can run off in another direction... nut in hand 🌰.
Check out this fascinating behavior
Delgado et. al., 2014; Steele et. al., 2014; Steele et. al., 2008
I spent the week in Minneapolis, Minnesota! I attended the International Society for Behavioral Ecology Conference, a meeting where animal scientists 🦁🐝🐍🤓from around the world 🌎meet to share their research 🔬⚗📈.
In honor of my trip ✈️, today’s Sunday Squirrel Spotlight star 🐿🌟 is the thirteen-lined ground squirrel (ictidomys tridecemlineatus)! These squirrels are abundant in Minnesota and can be found on grasslands and prairies 🌾.
Thirteen-lined ground squirrels have quite a few nicknames, including the striped gopher and the leopard ground squirrel. These elaborately decorated cuties live solitary lives in burrows deep underground that they also use for food storage and hibernation. These sneaky squirrels have also been observed creating “emergency burrows”, or shallow holes in the ground that can be used to make quick escapes from snakes 🐍and falcons 🐦.
Thirteen-lined ground squirrels are tasty snacks 🍗🍕 for birds of prey like owls, as well as coyotes and snakes. When they are above ground foraging it is important for individuals to be able to accurately read signals from the environment , because potential danger may be lurking 👀.
To keep safe these striped squirrels have two primary strategies. First, they tend to forage close to burrow entrances. This allows them to make quick escapes if a predator shows up. Second, thirteen-lined ground squirrels will visually scan their environment looking for predators 🐍👀.
One study found that these squirrels preferred not to forage further than 2 meters (6 feet) from a burrow entrance, and the presence of a plastic owl in the area resulted in squirrels foraging less and hiding more.
Thirteen-lined ground squirrels are solitary and do not always warn others when they detect predators. Mother squirrels however, have been found to sound the alarm by calling to their foraging babies. These same squirrels will not call if their litter is not out foraging and single males and non-breeding females tend to alarm call less.
Here is a short video demonstrating this alarm calling behavior!
Cleary & Craven, 1994; Thorson et. al., 1998; Schwagmeyer, 1980
The first step to squirrel gazing 🐿👀 is attracting squirrels!
This is usually done by handing out snacks to these furry foragers. 🌰
But, what should you be filling your feeders with?
To find out what wild squirrels like to eat 🍕🍪🍿 I went to my local grocery store and purchased a sampler of every type of nut and seed they had! (This does get you some weird looks at the checkout stand! 💁🏻👀)
Next, I counted out 40 of each food type, mixed them all together, and placed them on a tray. It’s like a squirrel Hometown Buffet.
Let the food preference test begin!
Everyday for six days, at 5pm I would place the tray at the base of the favorite tree of my loyal crew of 12 fox squirrels 🐿in the botanical garden 🌻🌲 on the UCLA 🐻 campus .
The tray would remain in the garden for two hours. At the end of which I recorded how many pieces of each food type was left behind. 🌰
The results are in! 🔎 📊
The favorite food of the UCLA botanical garden fox squirrels (Sciurus niger) are Walnuts! Followed closely by a tie between peanuts and hazelnuts.
Close to 80% of all the walnuts placed on the food tray over the six testing days were chosen by the squirrels. Compare that to the least liked food, sunflower seeds 🌻, where only about 10% of the items were taken!
The information I gained by completing this food preference test will help inform what types of squirrel snacks I should fill my data collecting feeder with!
Here is a video montage of squirrels selecting their favorite foods! 🐿👀🎥