It's Lambing Season in Anza-Borrego!

This is a long one, folks… Get ready!

Yesterday, I got to sit in on a presentation that Janene Colby, a wildlife biologist for the CA Dept of Fish & Wildlife, gave to the AmeriCorps Crew we have here in Anza-Borrego. She spoke of her career path, her current position as a wildlife biologist, and an overview of the natural history of the Desert Bighorn Sheep. It was a hugely informational presentation for me and judging by the questions from the crew, it was worth their while as well. So let’s get to it!

Photo by Faye Dorsey

Spring is a beautiful time… the time of the cute baby animals. If you’ve ever seen a picture of a Desert bighorn lamb, you know what I’m talking about. They are, in a word, adorable. And this is their time of year. Lambing season in Anza-Borrego is typically February through April (January to February in Palm Canyon) and the first year is often one of struggle and (hopefully) triumph. But first, let’s back up a bit.

Desert Bighorn Sheep is one of three subspecies of North American sheep. Before 1993, our population here in the Peninsula range was considered a separate subspecies below the Desert Bighorn. Now (although often still called Peninsular Bighorn Sheep) they are recognized as Desert Bighorn Sheep in scientific research, the same species that exists in the Mojave area and over in Arizona. The Peninsular Bighorn Sheep were federally listed as an endangered segment of the species in 1998 because their numbers here in the Peninsula range were very low. Why? Due to habitat loss and fragmentation resulting from human encroachment, disease, insufficient lamb survival, and predation coinciding with decreased population numbers. Since 1998, Desert Bighorn Sheep numbers in the area have risen from 334 to 955 in 2010. Sounds pretty good, right? It is, but although their numbers are on the rise, there is still cause for concern for the species. 

I mentioned that one reason for our population being federally listed was insufficient lamb survival. This is called recruitment, and we’re talking mostly within the first year. A really good, healthy survival rate for lambs is about 30%. In 2013, the survival rate sat at only 10%. But why? If they are protected and we’re helping to manage their populations, why is that survival rate not much higher? The simple answer (if there ever is one- keep in mind there are a lot of other factors at play here) is disease. Adult females are carriers of a bacterial infection that does not seem to bother them. Ever seen a ewe coughing up in Borrego Palm Canyon? This is probably why. The lambs are getting this bacterial infection from their mothers. It progresses into a kind of pneumonia, characterized by coughing, diarrhea, droopy ears, malnourished body types, and lethargic behavior. These signs of sickness usually start around 2 weeks after birth and if the lambs die, they will typically die between 8-10 weeks after birth. Lambs that survive are able to do so by consuming enough water and keeping their body weight up. 

Photo by Faye Dorsey

And now for my words of caution, echoed from Janene: Stay on the trails in known sheep areas, especially Borrego Palm Canyon. Give all of the sheep a wide berth if you must go near them to keep hiking. If the lambs are sick, they will try to stay down near the water as long as possible. If people are constantly approaching, they may get scared and use up the little amount of precious energy they are able to muster, wasting it trying to stay away from humans. It may seem that your presence doesn’t bother the sheep, but I can guarantee you, it does. So keep your eyes open when hiking in canyon bottoms in spring, especially during lambing season. 

I could go on forever, but I suppose I should finish up soon here. Once the lambs are born, the ewes will stick together in a nursery system. Each ewe only has one lamb, but they will often “babysit” so that all of the ewes are able to go find water, food, etc. Rams have nothing to do with raising lambs… the ewes raise their lambs together. They nurse for about 6 months (which brings us to about August), just in time for the rut. The gestation period for sheep is 6 months. So basically, the ewe is working all year long. They give birth in February, stop nursing in August, the rut (mating season) is from about June-September, then their gestation brings them to February! Non-stop working mommas! Where do the men go once the rut is over in September? Bachelor groups. Typical.

Photo Credit Unknown

So when you’re out and about in Anza-Borrego, whether it be on a road, trail, or cross-country, keep your eye out for the ewes and lambs and give them their space. Sheep like road cuts, as well, since the rocks are typically a lighter color there, so SLOW DOWN on the roads. They live here, we are simply visitors. 

I’ll stop there but rest assured, I’ll be back sometime in the future with more on the natural history of the Desert Bighorn Sheep. We’ve been heavy on the adventure and lacking on the education with our blog… I’m working on fixing that!