Study finds orphaning stunts growth in wild African elephants
Contact for reporters:
Nik Olsen
nik.olsen@colostate.edu
Orphaned animals of several mammal species suffer socially and physiologically, and even if their mother dies after weaning, they may have lower survival than non-orphans. One physiological consequence of orphaning – stunted growth – had been discovered in humans and chimpanzee orphans. A new study, published recently in the journal Conservation Physiology, shows that orphaning also stunts the growth of African elephants by an estimated average of 13 centimeters.
The new research, conducted by Colorado State University, Save the Elephants and San Diego Zoo Wildlife Alliance, found that orphans are shorter for their age than non-orphans. Stunted growth is of special concern for endangered elephants because growth positively correlates with fitness. Researchers used laser rangefinders to measure heights of 59 individually known wild female elephants, 32 orphans and 27 non-orphans in Samburu National Reserve of northern Kenya, home to Save the Elephants’ research camp.
Poaching of elephants for their ivory has led to dramatic reductions of elephant populations across Africa, most recently between 2009 to 2016. Elephants are highly social, maintaining life-long bonds with their family members. Poaching dramatically disrupts these important relationships, mainly by removing larger, older individuals from families. While much work has been done quantifying levels of illegal killing and subsequent impacts on population numbers, little was known about the longer-term ramifications for survivors of poaching sprees. Long term studies of the Samburu elephants are offering unique insight regarding orphaned elephants that grow up without their mothers.
While growing up without their mother’s milk might seem like the obvious reason for the orphans’ stunted growth, researchers say it isn’t so. All but three of the 32 orphans studied in the research were fully weaned when their mothers died. Rather, they believe it is likely due to a lack of access to adequate nutrition. This is because orphan calves don’t have their mother to keep older, more dominant elephants from pushing them away from optimal plant food sources. Stress from the experience of losing a mother and living without her care may also play a role, as stress and lower body mass are known to coincide, and stress hormones often coincide with lower levels of growth hormones.
This study also coincides with research released last month from CSU and Save the Elephants, which showed elephants with more age mates in their core family have lower average levels of stress hormones; having more age mates correlated with slightly greater growth for the measured elephants. It is coming to light that “friends” are important to the physiological well-being of young elephants.
“While non-orphans spend their days very near to their mother for at least the first nine years of life, orphans have lost their mother’s constant protection, guidance and companionship,” said lead author, Jenna Parker, NSF postdoctoral research fellow in biology with San Diego Zoo Wildlife Alliance. “The difficulties of losing this vital relationship are measurable, as orphan elephants who were weaned at the time of their mother’s death are significantly shorter than non-orphans of the same age.”
“This work highlights the longer-term implications of highly stressful events, like poaching epidemics or severe droughts, on surviving elephants. We often overlook the nuanced behavioral ramifications of these events in favor of the raw counts of elephants left standing. But in a highly cognitive and social species like elephants, the loss of family members and social bonds can itself be detrimental,” said George Wittemyer, professor at CSU and chair of the scientific board of Save the Elephants.
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About Save the Elephants
Based in Kenya, Save the Elephants works to secure a future for elephants. Specializing in elephant research, they provide scientific insights into elephant behavior, intelligence, and long-distance movements and apply them to the challenges of elephant survival. Education and outreach programs share these insights with local communities as the true custodians of this rich heritage. The team works towards a future of harmonious coexistence between humans and elephants. High-tech tracking helps plan landscapes while low-tech beehive fences, among other tools, provide farmers with protection as well as income. To battle ivory poaching, Save the Elephants teamed up with the Wildlife Conservation Network created the Elephant Crisis Fund to identify and support the most effective partners in Africa and in nations with ivory markets to stop poaching, thwart traffickers and end demand for ivory.
About San Diego Zoo Wildlife Alliance
San Diego Zoo Wildlife Alliance is a nonprofit international conservation leader, committed to inspiring a passion for nature and creating a world where all life thrives. The Alliance empowers people from around the globe to support their mission to conserve wildlife through innovation and partnerships. San Diego Zoo Wildlife Alliance supports cutting-edge conservation and brings the stories of their work back to the San Diego Zoo and San Diego Zoo Safari Park—giving millions of guests, in person and virtually, the opportunity to experience conservation in action. The work of San Diego Zoo Wildlife Alliance extends from San Diego to strategic and regional conservation “hubs” across the globe, where their strengths—via their “Conservation Toolbox,” including the renowned Wildlife Biodiversity Bank—are able to effectively align with hundreds of regional partners to improve outcomes for wildlife in more coordinated efforts. By leveraging these tools in wildlife care and conservation science, and through collaboration with hundreds of partners, San Diego Zoo Wildlife Alliance has reintroduced more than 44 endangered species to native habitats. Each year, San Diego Zoo Wildlife Alliance’s work reaches over 1 billion people in 150 countries via news media, social media, their websites, educational resources and the San Diego Zoo Kids channel, which is in children’s hospitals in 13 countries. Success is made possible by the support of members, donors and guests to the San Diego Zoo and San Diego Zoo Safari Park, who are Wildlife Allies committed to ensuring all life thrives.
About Colorado State University
Colorado State University is one of the nation’s top public research universities and an institution on the rise. In the last decade, CSU has produced record enrollment, built on all-time highs in student diversity and student success; record fundraising far outpacing ambitious goals; groundbreaking research driven by a highly productive faculty; a campus revitalized by a transformational building campaign; and rose to be a global leader in sustainability. It is an unrivaled learning environment where nine of 10 recent graduates say they would choose CSU again and rate their education as excellent. CSU’s research expenditures exceeded $447 million last year and the institution is a leader in areas such as atmospheric science, energy, water, veterinary and translational medicine, natural resources, chemistry, occupational therapy, and anthropology, and with ongoing and traditional strength in areas such as engineering and food production. CSU is part of the Colorado State University System.