Effects of Predator Scent on the Foraging Behavior of Acomys cahirinus
Acomys cahirinus, more commonly known as spiny mice, were tested to see if they would prefer to eat a high reward food if it was placed near the scent of the allopatric predator Felis catus (a domesticated cat) or food away from the scent. The results show that the spiny mice did not have a significant preference to the placement of the food (p-value 0.18)
Key terms: Acomys cahirinus, Felis catus, predator scent
Animals use chemicals and scent for a variety of methods of communication such as pheromones for mating, chemicals to ward off predators or urine to mark territory. In addition to these uses of chemicals, many animals may use chemosensory detection as a way to avoid predators (Epple, et al. 1993). For example, Epple et.al.(1993) found that mountain beavers (Aplodontia rufa) were significantly less likely to eat an apple from a bowl covered with scent from the anal glands of its natural predator the mink than apples covered in butyric acid. This same trend was found when snowshoe hares (Lepus americanus) avoided eating seeds covered in Gulo gulo(wolverine) urine (Sullivan1986). Based on this evidence, we predicted that a Acomys cahirinus (spiny mouse) would prefer to feed on a high reward food in the absence of cat urine rather than on a high reward food in the presence of cat urine. Spiny mice are nocturnal dwellers that tend to have a high giving-up density because they are inefficient foragers (Jones et al. 2001). They will also change their foraging behavior seasonally to compensate for predation risk (Jones et al. 2001).
On 19 and 21 March 2007, nine spiny mice were tested to see if there was a preference in foraging environment. The two foraging environments consisted of either having cat urine or no cat urine within them. The mice fasted 48 hours before each trial and each was tested twice, one trial per day. A clear, plastic Y-maze with a parameter of 252.3cm and height of 15cm was used (Fig. 1). Each end of the Y-maze had 11 sunflower seeds in total. One sunflower seed was placed towards the opening of each end, to aid in luring mice to 10 sunflower seeds at the end (Fig. 2). The urine was collected prior to the study on an old T-shirt and cut to size for the maze. A 4cm by 4cm cloth saturated with cat urine was put on cellophane and randomly placed on the right or left side of the maze. This was assigned by drawing a piece of paper that either said left or right side on it. Each experimental trial was timed for 5 minutes. Observations were recorded during each trial. At the end of each trial, remaining sunflower seeds were collected to figure out how many seeds were consumed on what side by the mouse. An independent, 2 tailed T-test was performed to analyze data. Microsoft Excel was the program utilized in this analytical process.
Figure 1. Dimensions of Y-maze
Figure 2. Dimensions of experimental set up
There was no significant difference in preference of foraging microhabitat (with or without cat urine) by spiny mice (Fig.3, P = 0.18). However, the side with cat urine was chosen the most for consuming sunflower seeds (Mean = 2.3, S.D. = 3.3), and the side with out urine was chosen the least (Mean = 1.1, S.D. = 1.9).
Figure 3. Average number of seeds consumed by spiny mice in presence of urine scent and without urine scent.
The results of the experiment showed no significant difference between the spiny mice’s preference of food when exposed to the cat urine. The results may be explained by a two possible factors. Carnivore urine contains different scents than non-carnivores (Epple et al. 1993); however, the diet of cats used contained mainly vegetarian ingredients which may have reduced the effectiveness of the urine. In addition, an introduced predator may be less effective than a natural predator (Banks 2006). Banks (2006) found while trapping bush rats (Rattus fuscipes) in traps with no odor and traps with an odor of an introduced predator (Vulpes vulpes), no significant difference was found. Similarly, Epple et al. (1993) found that animals more effectively respond to sympatric predators than allopatric predators. Future studies may account for these variables by testing the mice response to the urine by using urine from a carnivore or by testing the variability of the response of the spiny mice to a natural predator verses a domestic cat.
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Epple, Gisela; Mason, J. Russell; Nolte, Dale; Campbell, Dan (1993). Effects of Predator Odors on Feeding in the Mountain Beaver (Apiodontia rufa). Journal of Mammalogy. Vol. 74. No. 3. pp. 715-722. Retrieved from www.jstor.org on 3/26/07.
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