Guess Who Is Coming to Your Backyard 2?

By AdminBirds, Camera Traps, Conservation, Conservation Science Investigators, Education, Little Green Guards®, Mammals, Plants, Research, San Diego, USA
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Written by Julian, Little Green Guards® C.S.I.

 

INTRODUCTION

In my previous blogs I reported on camera trap studies I conducted in my backyard, a surrounding golf course, and a nearby avocado grove that is next to coastal sage scrub habitat. My studies generated buzz around the neighborhood, and from local residents I found out about other wildlife sightings in their backyards – including an American badger (Taxidea taxus), a carnivore in the weasel family (Mustelidae) that is very rarely seen in Southern California. One person came across the “Have you seen a badger?” poster on the United States Geological Survey website, and after reading about how everyday citizen can help find this elusive animal, I was inspired to do another C.S.I. study using camera traps.

My study was conducted in the backyard of the neighbors who had reported the badger sighting. I hoped the results would answer several questions. First, I wondered how many new species, beside the badger, I might find? My second question was how much time would be needed for the camera traps to record all small- and medium-sized mammalian species in the area? To find out my mentors showed me how to estimate minimum trapping effort, which tells me the least amount of time needed to complete an inventory of target species in my neighborhood.

 

METHODS

The neighbors’ backyard is located just above the avocado grove where my last study took place.

 

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A map of my study sites (© LVDI International)

 

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This backyard is mainly a concrete patio with a few plants. On the left, hidden behind a shrub and next to a stone pagoda, is a fountain. Note: there is no fence separating my neighbors’ property and the grove below (© LVDI International).

 

I monitored the backyard during four periods: 9/9/20 – 9/17/20, 9/17/20 – 9/21/20, 9/22/20 – 10/6/20 and 10/9/20 – 10/12/20, for a total of 31 trap days. During the first period two cameras were used, but afterwards only one was needed to avoid duplication of effort. Although I did not make any direct observations, I included in my results any wildlife sightings by local residents during this time.

The camera traps were programmed the same way as in my previous studies. I also analyzed my data following the same methodology as before. To determine the minimum trapping effort, I made a species accumulation curve based on the number of camera days and the cumulative number of species that were captured in the photos. When all species have been recorded, the curve will plateau.

 

RESULTS AND DISCUSSION

A total of 2,563 photos were taken. There were at least nine mammal and three bird species captured by the cameras. The newly recorded species included the raccoon (Procyon lotor), California ground squirrel (Otospermophilus beecheyi), Virginia opossum (Didelphis virginiana), black rat (Rattus rattus), mourning dove (Zenaida macroura) and Anna’s hummingbird (Calypte anna).

 

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I was surprised to see many different animals visiting my neighbors’ backyard. Shown here are: 1) striped skunk, 2) coyote, 3) raccoon, 4) human, 5) mule deer, 6) California ground squirrel, 7) Virginia opossum, 8) black rat, and 9) mourning dove (© LVDI International).

 

One reason more species were recorded in this study than in my previous studies was because the monitoring period was longer. Another reason could be because of the availability of a particular resource. I noticed that almost all images recorded the animals either approaching or at the fountain. Therefore, the main attraction for the animals was probably fresh water.

 

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In one event a group of four mule deer spent over 23 minutes in the backyard, taking turns to drink from the fountain. Here, on the right, the camera captured a fully mature buck for the first time (© LVDI International).

 

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Independent events involving humans were the highest among all species recorded by the camera traps. This was because the homeowners performed daily activities in their backyard, including changing the water in the fountain twice a day (© LVDI International).

 

If you recall, the bobcat (Lynx rufus) was seen in the avocado grove. Although I did not find the animal this time, a neighbor several houses away kindly shared with me an extremely rare video of a female bobcat taking her playful kittens on a morning stroll.

 

 

The animal that obviously was missing from my camera trap photos was the American badger. Why did it not appear? After doing some reading, I learned that badgers tend to be solitary animals that prey on squirrels and other small rodents. Each individual can have a home range of up to 3.3 square miles1, 2. I suspect that the individual that was observed by my neighbors was probably moving through its home range. So even if I had left the cameras run for a very long period, I still might not have recorded a single badger. In fact, documenting this species’ presence in Southern California has proven to be quite difficult. It took one conservation group three years to obtain undeniable photographic evidence of the badger in Julian, a town in San Diego’s East County3.

When researchers consider using camera traps in their studies, they need to think about where to put up the cameras, when to put them up, and how long to have them record.

 

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In my multi-part studies, I focused on habitat characteristics and found spatial variations in species composition as well as their capture rates. The study sites had different available resources (i.e. food, water and shelter) and human disturbance levels, and even within each site resources were not homogeneous (© LVDI International).

 

Another common theme throughout my studies was the variation in daily activity patterns among species – some animals are diurnal; some are nocturnal and some are active both day and night. In terms of temporal variations, what I have not examined are seasonal changes. Both temperature and rainfall can affect species composition. If my studies were done during winter, I would not see hibernating or migratory species. In Southern California, the majority of rain comes in January-April. For animals that rely on plant food, their reproduction is typically tied to the rainy season when new vegetation grows the fastest.

 

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The California ground squirrel hibernates in the winter. Females produce pups in the spring when plant food is most plentiful (image from Pixabay).

 

In this study, the most common animals – skunks, coyotes, raccoons and squirrels – were recorded during the first few days. By Day 4 over 80% of the species present had been recorded by the camera traps.

 

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Only three more species were added to the total over the next 27 days. The minimum trapping effort was estimated to be 18 days, when the curve reached a plateau. If I had cameras monitoring different sites over an entire year, the species number would be higher and the curve would be smoother (© LVDI International).

 

CONCLUDING REMARKS

During my studies I learned that camera traps are very useful for tracking certain mammalian and avian species that occur around my neighborhood. That is because they operate continuously and animals don’t notice them like they would a human observer. However, detection of individual species by camera traps is not always perfect. That is why local residents can serve as “citizen scientists” to help with wildlife inventories, particularly of rare and elusive species. Such inventories can be used to determine the health of a habitat, like the coastal sage scrub, where less than 15% of the original area remains in Southern California4. My studies can help raise awareness about the importance of conserving native habitat and species surrounding urban and suburban communities.

I also learned how to record and analyze data, make graphs and communicate my findings by writing science blogs. Overall, the C.S.I. program was a very good educational experience and I encourage you to try your hand at things like this.

Now that the studies have concluded, I would like to acknowledge some people. Firstly, I thank my mentors, Dr. Chia Tan and Dr. Andy Phillips, for training and guiding me through every step of C.S.I. They were very patient and taught me lots of things. I thank my mom for encouraging me and my grandmother for introducing me to LVDI International and the Little Green Guards®. Finally, I want to thank the neighbors who provided the valuable wildlife information that was included in this study.

 

Sources:

    1. Sargeant, A. B. and Warner, D. W. (1972). Movements and denning habits of a badger. Journal of Mammalogy 53: 207-210. 
    2. https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=2597&inline=1
    3. https://www.sandiegoreader.com/news/2017/oct/15/stringers-cheers-badger-den-near-julian/
    4. Noss, R. F., LaRoe, E. T. and Scott, J. M. (1995). Endangered Ecosystems of the United States: A Preliminary Assessment of Loss and Degradation. Biological Report 28. USDI National Biological Service, Washington, DC. 

 

Julian is a 5th grade student in San Diego County.