Spring, Glorious Spring

Finally, spring has arrived in the Limay River Valley! It has turned wonderfully warm, so warm that the wind is a welcome friend. We’ve had a few sprinkles of rain but the temps are good enough to take a bath in the stream. We are now upon our last week of field work for C. sociabilis. It has been an interesting field season, surprising with who we’ve found has survived. Overall, older females seemed to do better than yearlings and even more of a surprise, there has been an adult male in nearly every colony! Those of you who know the tuco-tuco story know that male survival is quite low in this species, and in fact, we rarely encounter an adult male. It’s a good year when about 40% of the colonies have a male. So why such a difference this year? While they had rain in May (their Fall), they had little rain through the winter when tucos are mating. Perhaps, mortality was very high for last year’s litters, but I’m not sure if lowered competition for the males gave those remaining a better chance at survival. Who knows? But we also have seen a strong male sex ratio bias in the pups. And finally, I have only come across one lone female. The rest are living in groups this year. I have seen this downward trend toward fewer and fewer females living alone over the past 6 years. I am anxious to go back over the data to see if there may be a pattern that emerges with weather, yearling survival, sex ratio and number of lone to group colonies.

Today’s photo show a little pup and his generous donation to my dissertation cause. I do need more than one poop to get a sufficient sample of CORT hormones but he came through with more! I’ve collected a fair amount of samples and will add it to what I’ve already analyzed in the lab. In general, I have found that group living females have lower baseline CORT (or stress) hormones than females living alone. I have also found that CORT in pups is also high or low depending on living with a lone mom or group living moms. How much of that is inherited or passed through mom’s milk is yet to be known, but it is interesting to me. With the help of the best undergrad “wranglers” ever, I continue to run behavior tests with the pups in the lab at Berkeley, looking to see if behavior and hormones are correlated. Specifically, I am testing exploratory or bold behavior in an open arena in which they have the option of running around or hiding in a refuge. We have found in the adult lab females that there’s a strong correlation with CORT and boldness. That is, lower CORT, higher exploratory behavior. We’ll see how this holds with the pups.

We leave in about 5 days for a place called Chubut to check out a possible population of C. sociabilis. It’s been rumored that there use to be some living in this region south of Bariloche. We’ll be breaking camp on the 15th, head down to Chubut for a few days and then back to Bariloche, where we catch the bus to Salta. There we will rent a truck and head into the mountains near Jujuy and I will get to meet another social tuco-tuco!