Peninsular Desert Bighorn
Ovis canadensis nelsoni
Amy Sublett
Description and Ecology of Organism
Ovis canadensis nelsoni is one of three subspecies of bighorn sheep living in North America, two of which are present in California, the other being Ovis canadensis sierrae, the sierra nevada bighorn.
Peninsular desert bighorn sheep are most easily recognized by their curling horns, a bone-like structure surfaced with keratin, as well as the contrasting white coloring of their rumps. Males (rams) and females (ewes) carry horns, though
those of the ram are much larger. A ram’s horns are an indication of its status in the social hierarchy and the animal’s age, because they grow continuously throughout an animal’s lifetime. Males assert their dominance through “clashes” to win the attention of females and obtain ideal bedding sites. Peninsular desert bighorn sheep present dark brown or grey colored coats, though in comparison to other desert bighorn sheep their coats are paler and their horns larger and heavier. In all, when compared to populations of bighorn sheep found in more northern regions, desert bighorn sheep are smaller in stature with a sleeker coat.
Individuals are approximately 30-39 inches tall, when measured to the height of their shoulders, with rams weighing about 160 pounds and ewes weighing near 105 pounds. Ewes live 12-20 years, while rams typically live 10-13 years. Peninsular desert bighorn sheep inhabit rocky slopes and cliffs, canyons, washes and alluvial fans. Like other bighorn sheep, they prefer rugged and open habitat, and use their climbing abilities, excellent vision and well-adapted hooves to detect and escape from predators.
Geographic and Population Changes
This population of sheep is one of the largest contiguous metapopulations of desert bighorn sheep, occupying approximately 100 miles of habitat. Attempts to conserve the species began in the 1970s with their legal protection under California State Law. However, when the population declined from approximately 1,100 individuals when they first became protected to 400 by the year 2000, it became evident that greater changes needed to be made toward its protection. Peninsular desert bighorn sheep are generalist herbivores and consume a range of desert plants, including cacti. Regardless of their broad diet, the activities of the surrounding land and development are making resources and quality habitat scarce.
Listing Date and Type of Listing
Listing: Endangered
Date: March 1998
Cause of Listing and Main Threats to its Existence
Some of the greatest threats to this population include habitat modification, degradation and fragmentation due to human encroachment. Similarly, the development of roads and railways through their habitat, livestock grazing and risk of disease introduction by livestock generate large risks to the population’s success. Additionally, fire suppression and mountain lions threaten the species, two things a robust population would be able to withstand.
Description of Recovery Plan
The recovery plan, drafted in 2000, after the species was labeled endangered, states that before the population can be declared as stable, a minimum of 25 ewes must be present in each region marked for recovery, spanning Imperial, Riverside and San Diego counties, for 12 consecutive years. Holistically, the rage must host an average of 750 individuals with a stable and increasing population trend over the same 12 years. However, regulatory systems and management practices have been established to provide long-term protection of the species and its essential habitat. Another goal of the of the recovery plan is to reduce habitat fragmentation in the region to allow members of the species to move freely through the Peninsular ranges. Currently, each subpopulation is monitored and a range-wide biennial analysis is produced. Since the commencement of this systematic species monitoring in 2000, the range-wide population is observed to have increased to 955 individuals as of 2010.
What Can You Do?
One of the greatest things we can do to help is to spread knowledge of the species and its threats. Much of the habitat degradation experienced is directly correlated with human habitation of the surrounding region. It is important that we be aware of not only the primary habitat of the species itself, but how our lifestyle habits, including our pets, farm animals, crops and even landscape plants can indirectly affect peninsular desert bighorn sheep and similar species.
Other Resources
References Used
Esther Rubin. “Recovery Plan for Bighorn Sheep in the Peninsular Ranges, California.” (2000). U.S. Fish & Wildlife Services. U.S. Fish & Wildlife Services. Web. 9. Nov. 2017.
“Peninsular Desert Bighorn Sheep Conservation.” California Department of Fish and Wildlife. Web. 11 Nov. 2017.
Photographs:
1) https://www.wildlife.ca.gov/portals/0/Images/Nongame/BighornSheep/Peninsular/DesertRams.jpg
3) https://www.wildlife.ca.gov/Conservation/Mammals/Bighorn-Sheep/Desert/Peninsular/Range
4) http://www.desertsun.com/story/news/environment/2015/05/28/coachella-valley-peninsular-bighorn-sheep/28127119/
Great blog. It's unfortunate that all the things that benefit humans seem to do the opposite for every other living thing. I'll try to keep how my lifestyle is affecting the bighorn sheep, especially since I live somewhat close to Riverside. - Jacob Lafarga
ReplyDeleteThis was a really interesting blog to read. I appreciated the underlined sections of the recovery plan, which really helped with visual clarity. It was interesting to learn what a large area the metapopulation of bighorn sheep occupy, I had no idea it was so large. - Sophie Topping Zimmerman
ReplyDeleteAwesome blog! Really cool that their habitat can spread almost 100 miles long. Had no idea they had exisiting habitats in places so close to me. Definitely need to be more aware of how I could possibly effect these sheep and other animals alike. -Daniel Tomer
ReplyDeleteGreat blog! What I thought was crazy was how long they had been listed for. Almost 20 years now! Thats literally crazy. Like, somehow over 20 years we still haven't been able to take it off the list. Just goes to show how tedious the conservation process is. - Grantland T
ReplyDeleteNice job! I think it's really interesting looking at the recovery plan and how that will affect human development in the future. If we reduce habitat fragmentation, then hopefully populations can recover. -Alyssa Slattery
ReplyDelete