The Effects of Moon Phase on Southeastern Mesocarnivore Activity

C Forehand, C Marneweck, D Jachowski, S Harris

Abstract

  • To investigate the influence of changing moon phases on spotted skunk activity, especially considering their overlap with other carnivores, data from camera traps was extracted for the winter seasons of 2012-2017. A Watson-two test and pairwise comparisons of spotted skunk activity with other carnivore species revealed spotted skunks reduce their activity most around midnight during new moon and spotted skunks shift their activity during full moon to avoid bobcats.

Introduction

  • Changes in moon phase and moonlight lead to changes in predation risk and hunting efficiency1.
  • The individual species’ response to moonlight is affected by trophic level, sensory systems, habitat, and phylogenetic relatedness1,2.
  • Many studies have documented the effects of moon phase and illumination on herbivore behavior, yet few focus on the effects upon predators, and specifically carnivores that are also preyed upon, such as spotted skunks3.

Materials and Methods

  • Data from camera traps throughout the Southeastern US was extracted for the winter seasons of 2012 – 2017.
  • Watson-two test to determine if spotted skunk activity differed between new moon and full moon, as well as if spotted skunk activity differed from other carnivore species throughout the moon phases.
  • Performed pairwise comparisons of spotted skunk activity with other carnivore species to determine the coefficient of overlap.

Results

  • Spotted skunk activity significantly differed between new moon and full moon (w = 11.6225, P < 0.001). Spotted skunks most drastically reduced activity during new moon at midnight when it is darkest
  • Throughout both new moon and full moon, spotted skunks had the lowest overlap with red foxes and bobcats.
  • Overlap plots of spotted skunk and bobcat activity revealed spotted skunk activity shifts during full moon to overlap less with bobcat activity.

Figure 1. Spotted Skunk activity during full moon (i.e. high illumination; left, white polygon), followed by spotted skunk activity during new moon (i.e. low illumination; right, gray polygon).

Table 2. Results of coefficient of overlap with confidence intervals and Watson’s two-test sample performed on pairwise comparisons between spotted skunks and other carnivore species.

Figure 2. Activity overlap according to moon phase between bobcats and spotted skunks.

Conclusions

  • Our findings conflict with other reports that spotted skunks increase their activity when it is darkest4,5.
  • Spotted skunks may rely on being either cryptic or conspicuous depending upon the local habitat, prey and predators6. Periods of greater illumination may affect spotted skunks differently depending upon if they are trying to remain more cryptic or conspicuous.
  • Spotted skunks prefer to rely on smell and hearing cues, but it may be more beneficial for spotted skunks to forage in periods of greater illumination when visual cues can be combined with smell and hearing7,8.
  • Bobcats may be a potential predator spotted skunks are attempting to avoid. Differing responses to moonlight may help facilitate coexistence between smaller and larger mesocarnivores and allow smaller to avoid predation/injury from competition9.

References

1Pratas-Santiago, L.P., Goncalves, A.L.S., Nogueira, A.J.A., Spironello, W.R. (2017). Dodging the moon: The moon effect on activity allocation of prey in the presence of predators. Wiley ethology. 123(6-7):467-474. 

2Prugh, L.R., Golden, C.D. (2013). Does moonlight increase predation risk? Meta-analysis reveals divergent responses of nocturnal mammals to lunar cycles. British Ecological Society. 83(2):504-514.

3Rockhill, A.P., DePerno, C.S., & Powell, R.A. (2013). The Effect of Illumination and Time of Day on Movements of Bobcats (Lynx rufus). PLoS ONE, 8.

4Benson I, Sprayberry T, Cornelison W, Edelman A, (2019). Rest-Site Activity Patterns of Eastern Spotted Skunks in Alabama. Southeastern Naturalist, 18(1)165-172. 

5Thorne, E., Waggy, C., Jackhowski, D., Kelly, M., Ford, W. (2017). Winter Habitat Associations of Eastern Spotted Skunks in Virginia. The Journal of Wildlife Management, 81(6): 1042-2050. 

6Caro T., Stankowich T., Kiffner C. & Hunter J. (2013) Are spotted skunks conspicuous or cryptic?, Ethology Ecology & Evolution, 25:2, 144-160. 

7Johnson-Ulrich, Z., Hoffmaster, E., Robeson, A., & Vonk, J. (2017) Visual acuity in the striped skunk (Mephitis mephitis). Journal of Comparative Psychology. 131(4), 384–389.

8Slobodchikoff, C. N. (1978). Experimental studies of tenebrionid beetle predation by skunks. Behaviour, 66: 313–322.

9Penteriani, V., Kuparinen, A., Mar Delgado, M.D., Palomares, F., Vicente López-Bao, J., María Fedriani, J., Calzada, J., Moreno, S., Villafuerte, R., Campioni, L., Lourenço, R. (2013). Responses of a top predator and a meso predator and their prey to moon phases. Behavioral Ecology. 173: 753-766.