Predator cue avoidance in grey squirrels (Sciurus carolinensis)

Student Spotlight - Sam Ashby

Undergraduate Research at the University of Reading

Email: sam.s.ashby@gmail.com    LinkedIn: https://www.linkedin.com/in/sashby2/

I am a postgraduate student at the University of Sussex, having recently graduated from the University of Reading with a BSc Zoology degree. My BSc thesis focused on grey squirrel (Sciurus carolinensis) ecology, specifically the avoidance of chemical cues and the landscape of fear (LOF) concept.

Background

Prey species use various cues to assess the risk of predation, including tactile, acoustic, visual, and chemical signals (Caro, 1986; Møller & Erritzøe, 2010). Evasion is the optimal anti-predation defence and reduces the likelihood of conflict. The landscape of fear concept proposes prey species will avoid foraging patches frequented by predators or predator cues (Bleicher, 2017). Few studies have simulated a landscape of fear through chemical predator cues. Our research aimed to quantify the shift in grey squirrel foraging in response to the chemical cues of native and invasive predators, pine martens (Martes martes) and domestic cats (Felis catus).

Methods

Several feeding stations were set up across the University of Reading campus, each positioned a short distance from remote camera traps. To simulate predator presence, chemical samples were prepared and placed within feeders. Squirrel feeders were manipulated to accommodate predator cue samples (Figure 1).

Pine marten presence was simulated with samples of a solution containing water and pine marten faeces. Cat presence was simulated with samples of diluted cat urine. Diluted domestic rabbit (Oryctolagus cuniculus) urine and distilled water samples were used as control samples.

The duration of feeder visits, the time spent feeding from within feeders, time spent resting and/or environment scanning upon the feeding platform, and time spent in proximity to feeders were recorded from camera trap footage (Figure 2).

Results

• Water and rabbit urine samples did not affect the duration of feeding, scanning, proximity, or total visitation.
• Feeding and total visitation durations decreased when cat urine was present.
• Pine marten faeces significantly reduced feeding duration compared to rabbit urine, but not compared to water.
• Pine marten faeces did not significantly reduce total visitation duration, compared to both control samples.

 

Implications

Grey squirrels were able to distinguish predator cues from non-threatening cues. This observation is coherent with previous research; predator urine contains increased concentrations of particular chemical components known as kairomones, such as 2-phenylethylamine, which helps rodents identify their presence (Ferrero et al., 2011).

The results emphasise the role of invasive cats as a predation threat to British wildlife. Though the grey squirrel is also an invasive species, future research may build upon these findings to demonstrate the effects of cat predation, or simulated presence, on native rodents.

Recently, the reintroduction of pine martens has been discussed as a means to reduce grey squirrel numbers. These results may be used as further motivation for pine marten reintroduction, since their presence is likely to reduce grey squirrel foraging and, ultimately, their fitness and abundance.

A simulated landscape of fear may be applied commercially; grey squirrels are often considered pests to arboriculturists and forestry industries due to their bark-stripping tendencies (Kenward & Parish, 1986). The implementation of predator cues may prove an effective deterrent of grey squirrels.

Project Highlights

This was a thoroughly enjoyable project and I’m glad I could combine the desk-based work with data collection in the field. It was really interesting to see how the squirrels responded to predator cues but, also, their interspecific interactions. Camera traps are a great way to see elusive wildlife and their behaviour. Some notable sightings included a muntjac deer (Muntiacus reevesi), great spotted woodpecker (Dendrocopos major), brown rat (Rattus norvegicus) and some amusing wood mice (Apodemus sylvaticus) trying to figure out the feeders.

 

Acknowledgements

I am grateful for the supervision and guidance provided by Dr Phil Baker, and the assistance in data collection provided by students Georgia Warren, Kathan Bandyopadhyay, and Aiden McCormick. Pine marten faeces samples were kindly donated by the British Wildlife Centre. 

If you would like more information on this research, please contact myself (sam.s.ashby@gmail.com), Georgia Warren (georgiawarren44@gmail.com), Kathan Bandyopadhyay (kathan1997@gmail.com), or Dr Phil Baker (p.j.baker@reading.ac.uk).

References

Caro, T.M. (1986) The functions of stotting – a review of the hypotheses. Animal Behaviour, 34, 649-62. https://doi.org/10.1016/S0003-3472(86)80051-3 

Møller, A.P. & Erritzøe, J. (2010) Flight distance and eye size in birds. Ethology, 116, 458-65. https://doi.org/10.1111/j.1439-0310.2010.01754.x

Bleicher, S.S. (2017) The landscape of fear conceptual framework: definition and review of current applications and misuses. Peer J, e:3772, 1-22. https://doi.org/10.7717/peerj.3772

Ferrero, D.M., Lemon, J.K., Fluegge, D., Pashkovski, S.L., Korzan, W.J., Datta, S.R., … Liberles, S.D. (2011) Detection and avoidance of a carnivore odor by prey.  Proceeding of the National Academy of Science, 108, 11235-40. https://doi.org/10.1073/pnas.1103317108

Kenward, R.E. & Parish, T. (1986) Bark-stripping by grey squirrels (Sciurus carolinensis). Journal of Zoology, 210, 473-81. https://doi.org/10.1111/j.1469-7998.1986.tb03650.x