Squirrel 08.mp4

Squirrel stories are thousands of years old. In Norse mythology, a messenger squirrel named Ratatoskr runs up and down the tree of life. The Choctaw tell of a black squirrel trying to eat the sun, causing a solar eclipse.

Squirrel 08.mp4

Is the hypothesis that a snake won't strike a tail-wagging squirrel because the individual has learned it is not effective or is it that reluctance to strike a tail-wagging squirrel is a behavior with a genetic component and the trait has proliferated in the population?

Dave, great question. I had no idea, so I asked Rulon. He says: "It's a question I'd love to answer. We don't have any data on how these behaviors develop in snakes ontogenetically, so I can't say if it's learned or not. My gut feeling is that it's probably a bit of both--they may show some reluctance to strike animals that appear to know they are there (through orientation, posture, etc), and then on top of this they probably rapidly learn that squirrels that tail flag in particular are very hard to land a strike on." So look out for future research out of Rulon's lab addressing this question.

He adds: "We do see snakes occasionally try to strike adult squirrels that are tail flagging, but they've always missed (one snake hit a tail flagging pup once, though). Thus, there appears to be lots of opportunity for learning from experience for the snakes."

Her legacy dates back to the 1970s. It all started on a whim when Best's father taught a rescued squirrel to water ski on a remote control boat. Seven generations of Twiggys later, her fan base keeps getting bigger.

When animals encounter a task they have solved previously, or the same problem appears in a different apparatus, how does memory, alongside behavioural traits such as persistence, selectivity and flexibility, enhance problem-solving efficiency? We examined this question by first presenting grey squirrels with a puzzle 22 months after their last experience of it (the recall task). Squirrels were then given the same problem presented in a physically different apparatus (the generalisation task) to test whether they would apply the previously learnt tactics to solve the same problem but in a different apparatus. The mean latency to success in the first trial of the recall task was significantly different from the first exposure but not different from the last exposure of the original task, showing retention of the task. A neophobia test in the generalisation task suggested squirrels perceived the different apparatus as a different problem, but they quickly came to apply the same effective tactics as before to solve the task. Greater selectivity (the proportion of effective behaviours) and flexibility (the rate of switching between tactics) both enhanced efficiency in the recall task, but only selectivity enhanced efficiency in the generalisation task. These results support the interaction between memory and behavioural traits in problem-solving, in particular memory of task-specific tactics that could enhance efficiency. Squirrels remembered and emitted task-effective tactics more than ineffective tactics. As a result, they consistently changed from ineffective to effective behaviours after failed attempts at problem-solving.

We further explored what retrieval strategy squirrels were employing in these two tasks by examining whether squirrels exhibited non-random changes in tactics or not. If squirrels have completely retained the learned task tactics they used to solve the original task, we predict that selectivity would remain at its highest (close to 1 as a proportion), whereas motor diversity, flexibility and persistence would remain at their lowest, and none of these traits would vary with increased experience (see situation 1 above). Such high selectivity would be expected to be one key behavioural trait that enhances efficiency in both tasks. However, as discussed above, if individuals have completely forgotten the task or only retained some information about the original task, then we would observe characteristic variations of these traits with increasing experience in the new situation (see situations 2 and 3 above).

Figure 1b, c shows the apparatus used in the generalisation task. It was a transparent puzzle box in the shape of a four-sided triangular prism (triangle front 35 19 18 cm; length width height, rectangular side 25 20 cm) with five levers inserted. The puzzle box had completely different physical characteristics and colour than the one used in the recall task, but it still involved moving levers, so that we could examine whether squirrels applied the learned effective and ineffective tactics to obtain the nuts. The length of the levers was shorter than in the recall task, and both ends of each lever were slightly curved (lever dimensions 23.5 2 0.2 cm L W H). The generalisation box had 5 holes (2 0.9 cm) on each side, which were horizontally but not vertically aligned with holes on the opposite side. Because squirrels showed a strong preference for choosing the functional levers (with hazelnuts) both in the original (Chow et al. 2016) and in the recall tasks (see results section), we further increased the difference between the recall and generalisation task by including only functional levers. As Fig. 1c shows, both lever ends protruded 1.5 cm out of the box. The box was supported by four wooden legs, creating a 3.5-cm gap from its base. The base of the box (32 10 3 cm) was a wooden sloped platform (in silver grey colour) which allowed a nut to roll down once it had fallen. As in the recall task, squirrels could see and smell the rewards but could not reach them directly. Squirrels were able to emit the same effective and ineffective behaviours on each lever to obtain a nut: pulling the near-end or pushing the far-end of a lever was ineffective, so they had to push the near-end or pull the far-end.

Squirrels first participated in the recall task, so we could examine whether they remembered the puzzle box they had experienced 22 months ago. The generalisation task was presented 6 days later so as to examine whether squirrels could transfer the same effective behaviours to a physically different box. We kept the same procedures as in Chow et al. (2016) for both the recall and the generalisation tasks; squirrels were tested individually to avoid confounding factors such as stimulus enhancement or social learning in the task. Each squirrel participated in three blocks of four trials in each task (for a total of 12 trials), with a 1-day break between each block (for a total of 14 testing days). In each trial, we placed the box at the centre of the test room. A trial started when squirrels touched or manipulated any part of the box. The trial ended when squirrels completed the task by obtaining all the rewards, when they had not touched the apparatus for 15 min, or when 45 min had elapsed, whichever came first. If a squirrel did not respond, we repeated the trial the next day. This only happened with one squirrel, Suzy, in one trial in the recall task. After every trial, we removed the odour left on the apparatus using disinfectant-impregnated cleaning wipes. We also used wipes after baiting in order to minimise any human scents left on the apparatus. For both tasks, the orientation of the apparatus and the direction the levers faced were pseudo-randomised between trials. For the recall task, we additionally randomised whether a given lever was functional or not. A single success at solving the problem was defined as a squirrel causing a functional lever and/or a nut to drop. A trial therefore normally consisted of five successes.

For both the recall task and the generalisation task, we measured the latency from when a squirrel entered the test room until it first used its nose or paws to touch the apparatus. We measured the contact latency on the last trial of the recall task and on the first trial of the generalisation task as neophobia. This allowed us to test whether the squirrels perceived the pyramid-shaped apparatus as a novel stimulus in the generalisation task.

We also measured the time taken to obtain each reward; this was used as a measure of problem-solving efficiency. Latency was timed from the moment when a squirrel started to manipulate a functional lever until the nut it contained dropped. Not every manipulation of a functional lever led to success, but the time spent in unsuccessful manipulation on it was still included. For each trial, we summed all the latencies on functional levers and then divided this total success latency by the number of functional levers that a squirrel solved during that trial, to obtain the mean latency to each success.

Persistence has been used to assess motivation (e.g. Biondi et al. 2008; Chow et al. 2016; Griffin et al. 2014). We measured persistence as the rate of attempting to solve the problem. An attempt was recorded whenever a squirrel used any of its body parts to manipulate a functional lever, regardless of whether the manipulation was exhibited as effective or ineffective behaviours directed at the box. A new attempt was counted when squirrels switched to a different functional lever or when the squirrel returned to manipulating the same lever after at least one second without having its body in contact with the lever. We counted the total number of attempts in each trial on all functional levers and then divided this number by the total success latency as defined above.

Figure 2a shows the median across squirrels of mean latency to success in the first trial (8 s) and the last trial (2 s) of the original task. Figure 2b shows the median across squirrels of mean success latency in the first trial of the recall task (3 s). Latency on the first trial of the recall task is significantly different from its value on the first trial of the original task (GEE χ 21 = 4.12, P = 0.032), but not different from its value on the last trial of the original task (χ 21 = 2.65, P = 0.104). These results indicate some retention for the task 22 months after the last experience with this box. The latency to each success did not vary significantly across trials in the recall task (χ 21 = 0.30, P = 0.587). 041b061a72