Behavioral Ecology Blog

So as many of you know, I have been having significant problems this spring with the mice. Basically, my dissertation depends on my being able to find breeding mice. This has been difficult… I work in the Sonoran Desert in Southern California, specifically Riverside county. Now California is in the middle of a severe drought, and unfortunately for me- one of the hardest hit counties is Riverside. The mice I study (Peromyscus eremicus) do not need water- ever, but they do eat things that do, plants. In addition to seeds, it is thought that they need some herbaceous plant matter especially around the time of reproduction. Winter/springs rains usually supply this- even in the driest of deserts… This rain didn’t come this year, and In dry years- they don’t breed. As the mice are not reproducing in Deep Canyon- I set out last week to find someplace they are… One of the 1st things I did was look at rainfall deficit- especially as it is relevant to mouse reproduction- the last 6 months. Now you will have to click on the map to see it, but this is a graphic of % of average rainfall for the past 6 months. 0% is BAD, and many areas in So Cal are there. What I noticed though, is that while all places are dry relative to average- that San Diego County (most south west corner of USA)- especially coastal San Diego is relatively wetter that the surrounding areas- so as a result, this was one of the places that I expected to be good.

So last week, I visited several places, and trapped in a subset of those… Unfortunately, some of the best prospective locations were unavailable. 2 (Snow Creek and Warner Pass) are owned by water companies- in regards to snow creek- I got the following humorous response to my request for access.

I’m sorry but in order to safeguard the public’s drinking water supplyto the greatest extent possible, we do not permit access to the SnowCreek area. I understand your desire to perform research, but forhealth, safety and security reasons, we cannot grant any exceptions.

OK… so I kid you not- this is likely one of the richest habitats in terms of fauna- forever closed off by fear of terrorist attack?? Potrero Creek, is apparently now a protected Wildlife area. I can get access there, but not without headache.. One problem though- is this sign that ominously labelled the entrance.. Hmm, Ballistics Testing???

OK, anyway- as this was an impromptu trip- I had NO camping gear… No nothing. So I slept in the backseat of the rental car- Wow- I know I used to do this when I was a kid, but let me tell you, that is NOt fun. I ate PB&J’s almost every meal for the 1st 3 days- then lived off of bananas, cookies, and peanuts… I had no cooler/ice, so I had not a single cold beverage for several days. I do not recommend this for desert camping..

The 1st place I went to- Echo Valley. A really nice place, ~5 miles north of Descanso California. I trapped off Boulder Creek Road, up a steep slope. Vegetation was fairly dense, although there were few rocky places… The Nolina was particularly pretty, and all the grasses were in bloom. It was obviously different that some other places in Riverside that were SO dry… I had really high hopes for this place.
In the end- with 60 small sherman traps, I only caught 2 Peromyscus- one P. californicus and 1 P. eremicus. The one eremicus I did catch was pregnant with 4 embryos- a great sign. I bet that if I spent a little time there and tried a few different locations, I would find success there..

From there- I went to Oak Grove- and spent 2 nights…. I trapped in the San Felipe Valley area, and one night in Oak Grove itself. MVZ researchers had been to both places in the 1930’s and found success.. Oak grove is notable for this sign.. I met neither pleasant people nor grouches… The only notable thing really was the campground- clearly constructed on a huge ant hill..

Fire Ants- Generally not to be contended with, at they inflict a bee-sting like bite usually with little to no provocation. Now these guys were really threatening, aggressive, and PLENTIFUL. The strange things though- they didn’t bite… Aggressive however, a different story. I spent all day holding my feet off the ground- the second I put the down- ants came crawling up my leg.. Weird.. Anyway, the mice were not so hot. Everything was bone dry and there were just very very few mice to be captured.

So the current plan is to re-group. Use the MVZ database to locate areas where there is high diversity, and use the precipitation data to select among possible sites. As it stands know- San Diego County is where it’s at..