Sunday, 12 July 2015

First Report on Camera Study - Badgers

A 365 day study of Badger (Meles meles) activity using a fixed trail camera: A short report

By Mark Smith

Summary

A Bushnell trail camera was installed on a regularly used track way in a hedge line between a wet meadow and arable field. The camera recorded 24 hours a day and all species triggered by the camera were recorded.
Badger data was collated to show overall seasonal patterns and changes in daily activity cycles. The data showed three main points relating to territorial behaviour and supported established research into Badger activity.
1.       Peak activity occurred in February coinciding with the birth of cubs underground prompting a strengthening of territorial boundaries reflected by increased transit past the camera as the boundary was patrolled and the edge latrine pit was visited more often
2.       Daily over night activity exhibited two peaks of activity in spring and summer relating to foraging and territorial behaviour interspersed with rest periods
3.       Frequency of activity was relaxed in the autumn and winter but the length of nightly activity increased up to 12 hours of activity per night in line with shorter days and the need to forage more to maintain bodyweight.
More analysis to compare year on year data is needed to improve the data set and specific studies of latrine pit  usage would enable a clearer picture of territorial activity to be assessed.

Introduction

Badgers live in social groups called clans of between 2 and 23 individuals (mean: 6). Badgers maintain a territory of 30ha in optimum habitat up to 150 ha in marginal ones (Harris & Yalden, 2008; Johnson et al, 2001). The boundaries of these territories are demarked by well worn paths and shared latrine pits. The size and configuration of the territory is determined primarily by the distribution of food (Harris & Yalden, 2008).
Badgers are mainly crepuscular and nocturnal emerging at around dusk and returning to their setts before sunrise (Neal & Cheesman, 1996; Johnson et al, 2001). In this short report the findings from a year long camera trap study of all species recorded moving along a hedge line have been analysed to investigate the activity of the badgers of a sett located 270m from the camera.

Methodology

Between the 21st April 2014 and the 19th April 2015 a Bushnell Nature View HD camera was placed on continuous record. The camera was set to record all animals and birds that passed its field of view. It was located at SP292671 (52.301295, -1.570757). The camera was mounted 1 metre off the ground on the trunk of a Beech tree and was orientated to face northwards facing along a well used track way in the hedgerow between a wet meadow and an arable field.
The camera was set to record 30 second video clips with a 1 second refresh time.
8MB SanDisk memory cards were changed every week and the clips reviewed. All species sighted and identifiable were recorded. Notes on specific behaviours were noted.
Over the year the camera was inoperable for 42 days. Outages were due to setting errors and battery failures. Total coverage is therefore 88.5% of the year. In this time the camera recorded 152 badgers. Individual badgers were not identified in this study, just presence/absence information.
Figure 1 shows a rough sketch map of the study area. The camera can be seen located on the hedge line and the sett further down the same hedge line. It highlights the main track ways used by the badgers and other mammals as well as key behavioural locations such as latrine pits and areas where regular foraging seems to take place.

Figure 1 Site Map showing camera location and points of interest

Results

The data from the study was tabulated in Excel and the formatted to express activity as an expression of the number of badgers recorded by the camera by week and each hour. In this way it is possible to map activity over the year and throughout the cycle of a day.
Figure 2 shows the activity over the year. Figures 3 - 6 shows seasonal differences in daily activity expressed as a mean number of Badger sightings per hour in each three month block.

Figure 2 Graph showing the activity of Badgers over the year


Figure 3 Daily activity cycle for Spring

Figure 4 Daily activity cycle for Summer


Figure 5 Daily activity cycle for Autumn

Figure 6 Daily activity cycle for Winter

Figure 2 shows a significant peak of activity in February and a smaller one in late April to May. The rest of the year activity was relatively stable.
The graphs for daily activity cycles indicate a range of patterns. Firstly autumn and winter activity is generally lower than spring and summer. Both spring and summer show two peaks of activity. In the spring these peaks are at 22.00 hours and 03.00 hours and for summer 22.00 hours and 04.00 hours. Daily peaks are less evident in the autumn and winter.
The length of activity across a day increases in length over the year between 8 hours in spring to 12 hours in the winter.

Discussion

The data collected in this study supports many of the findings of other researchers. It highlights specific peaks in annual patterns and difference between daily activity levels between seasons. This study, however, is different to other studies in that it focuses on a track way rather than a sett. This means that emergence times are unknown.  The camera is located between two latrine pits and on the border of a change in habitat. Badgers are known to operate bimodally, with activity either very close to the sett or removed from the sett especially along the boundaries, this is more pronounced in males (Revilla & Palomares, 2002; Roper et al, 1993) therefore this study explores the amount of time invested in maintaining a territory. The track way does not lead to established feeding grounds and foraging behaviour in the video clips was very restricted (only in the autumn) and most behaviour noticed was either direct transit along the track or marking.

Annual Pattern

The most obvious piece of data reflecting the badgers is the large peak in activity occurring in mid-late February. Here activity increased by 500%. This coincides with the time cubs are born in the setts (Neal & Cheesman, 1996)which is usually in the first three weeks of February (Harris & Yalden, 2008)).
Footage at this time reflected a general feeling of increased activity. Passage past the camera seemed quicker and more frenetic. There was also an increase in the amount of casual marking made by the males. It is suspected that the birth of the cubs promotes a level of excitement and activity in the clan. Sows that had just given birth are now able to come out and feed. They need to maintain their body weight in order produce milk. Boars, in a burst of protectiveness could be more actively demarking their territory to ensure the new additions and their home range are adequately defended. Research supports the idea that males are more active and travel (Neal & Cheesman, 1996; Revilla & Palomares, 2002)
Secondary smaller peaks in April and May likely coincide with the cub’s first emergence from the sett. No cubs were recorded on the camera as it is likely to far from the main sett although smaller individuals were observed later in the year. Emergence from the sett would free up sows from suckling duties and enable them to forage farther. The peak also corresponds to recorded activity peaks surrounding the main mating period in early spring (Harris & Yalden, 2008).

Daily Pattern

In all seasons the greatest level of activity is recorded 2-3 hrs after dusk this relates to their emergence time and reinforces work by Neal and Cheeseman (1996). As the camera is not at the sett but on a territorial route there is a delay in activity being recorded.
Badgers in spring tend to emerge around sunset and will forage around the sett a little before dispersing across a territory to feed and mark. A figure 3 show spring patterns of activity and shows two peaks of activity across the evening, 22hrs and 2am-4am. Two peaks reflect the recorded pattern of badger activity in which individuals will forage for a period of time have a period of rest before becoming active again just before returning to the sett (Neal & Cheesman, 1996) In this season females remain closer to the set (Roper et al, 1993) and males spend greater time using latrine pits and marking the territory (Revilla & Palomares, 2002). Spring has the shortest activity period at just 8 hours reflecting the females remaining either close to the sett, giving birth or males and females being engaged in mating activity.
Through the summer activity time increases to 10 hours a night and the likelihood of observation before sunset increases. This activity period is much longer than those recorded by Neal and Cheeseman (1996) which estimated total activity time to be approximately 6.5 hours. Like spring two peaks of activity occur over the night at 22 hrs and 4 am.
Autumn (Figure 5) shows the lowest frequency of activity and there is little evidence of any definite peak in the pattern of the night’s activity. Studies by Roper et al (1993) suggest that during the autumn male activity reaches a peak of activity along boundaries, establishing the territory ready to protect the foraging space for the winter, this data does not however support this. The degree of activity over the whole night is again longer that summer at 11 hours of activity, this could be related to the reduction in day length and the increase in foraging required to build up body weight for winter survival.
During the winter (Figure 6) activity over the night is at its maximum nearing 12 hours in total, with very little variation in the frequency of activity across the night. This is supported by data presented by Neal and Cheeseman (1996) which recorded 11 hours activity per night. Activity occurs between two hours after sunset and two hours before sunrise. 

References

Harris, S., & Yalden, D. (2008). Mammals of the British Isles: Handbook. 4th Edition. The Mammal Society.
Johnson, D., MacDonald, D., Newna, L., & Morecroft, M. (2001). Group size versus territory size in group-living badgers: a large-sample field test of the resource dispersion hypothesis. Oikos , 95, 265-274.
Neal, E., & Cheesman, C. (1996). Badgers. London: T&D Poyser Natural History.
Revilla, E., & Palomares, F. (2002). Spatial organisation, group living and ecological correlates in low-density populations of Eurasian Badgers (Meles meles). Journal of Animal Ecology , 71, 497-512.
Roper, T., Conradt, J., Christian, S., Ostler, J., & Schmid, T. (1993). Territorial marking with faeces in badgers (Meles meles): A comparison of boundary and hinterland latrine use. Behaviour , 127, 3-4.