Research Article: Creeping in the night: What might ecologists be missing?

Date Published: June 13, 2018

Publisher: Public Library of Science

Author(s): Carol Anne Nichols, Kathleen Alexander, Travis Longcore.

http://doi.org/10.1371/journal.pone.0198277

Abstract

Wildlife activity patterns tend to be defined by terms such as diurnal and nocturnal that might not fully depict the complexity of a species’ life history strategy and behavior in a given system. These activity pattern categories often influence the methodological approaches employed, including the temporal period of study (daylight or nighttime). We evaluated banded mongoose (Mungos mungo) behavior in Northern Botswana through the use of remote sensing cameras at active den sites in order to characterize early morning behavior for this diurnal species. Our approach, however, provided the facility to capture unexpected nocturnal activity in a species that had otherwise only been studied during daylight hours. Camera traps were deployed for 215 trap days (24 hour data capture period) at den sites, capturing 5,472 photos over all events. Nocturnal activity was identified in 3% of trap days at study den sites with both vigilant and non-vigilant nocturnal behaviors identified. While vigilant behaviors involved troop fleeing responses, observations of non-vigilant behaviors suggest nonresident mongoose may investigate den sites of other troops during nocturnal time periods. There was no association between the occurrence of nocturnal activity and lunar phase (Fisher’s exact test, n = 215, p = 0.638) and thus, increased moonlight was not identified as a factor influencing nocturnal behavior. The drivers and fitness consequences of these nocturnal activities remain uncertain and present intriguing areas for future research. Our findings highlight the need for ecological studies to more explicitly address and evaluate the potential for temporal variability in activity periods. Modifying our approach and embracing variation in wildlife activity patterns might provide new insights into the interaction between ecological phenomenon and species biology that spans the diurnal–nocturnal spectrum.

Partial Text

The categorization of wildlife activity tends to be constrained to traditional day-night niches, strictly classifying species as diurnal or nocturnal [1–3]. Less frequently, the term crepuscular is used, since many diurnal species are active at dawn and dusk as well as in full daylight [4]. Identification of distinct adaptations to either a diurnal or nocturnal life history strategy (e.g. larger orbits in nocturnal primate species improving night vision [5]) may contribute to the tendency by some to view species’ activity patterns as more of a binary trait, rather than extending across a spectrum of temporal activity types [2, 6]. The characterization of a species to an activity pattern may translate into a methodological approach where evaluation extending beyond the dominant activity period is never attempted.

From January to November 2016, nighttime activity was identified for 3% of the trap days (SD = 18%, n = 7/215) and across five of the 11 months of the study. Night trap events occurred between 2000 and 2400 hours (n = 7). The nighttime activity was observed in 29% of study troops (n = 5/17 study troops, S1 Table). There was no significance between land classification of the den site (town or park) and the occurrence of night activity (Fisher’s exact test p = 1). However, the limited number of park troops might have influenced our ability to detect an effect.

Like other social mongooses, banded mongooses are considered diurnal species [24] and, across studies, ecological and behavioral investigations have been restricted to daylight periods [16–22]. However, this limited temporal approach may fail to capture data critical to understanding the ecology, biology of a species, and the temporal nature of space use. Here, we report nocturnal behavior and space use for banded mongooses. Our observed nocturnal behaviors were both vigilant and non-vigilant in nature (S2 Table for ethogram). Where vigilance behaviors were identified, they were followed by fleeing and den relocation, which is unique for nighttime study periods in banded mongoose. Photos from the cameras traps did not, however, provide information as to what prompted these behaviors. Fleeing behavior in this species had only been previously been reported in association with intergroup aggression events [25].

 

Source:

http://doi.org/10.1371/journal.pone.0198277

 

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