Female Masai giraffes live in distinct social communities of up to 90 other friends, and although areas used by these ‘girl gangs’ often overlap, they have very different rates of reproduction and calf survival. This means the girl gang social units may be important to giraffe evolution. These findings were published this week in the Journal of Wildlife Management by a team of scientists from Penn State University and University of Zurich as part of the largest giraffe study in the world. “We used social network analysis of hundreds of females and discovered this girl gang social organization from the giraffe’s own preference and avoidance behaviors,” said Derek Lee, associate research professor at Penn State and senior author of the study. “Gang membership was pretty tight, and even though members of different girl gangs often spent time in the same areas, members of different communities rarely interacted with each other.”
The scientists further found that calf survival and reproductive rates were different among these social communities, even when communities’ home ranges overlapped in space and therefore shared similar environmental conditions. “This shows that population structure can arise from social behavior rather than discrete space use,” noted Monica Bond, lead author and research associate at the University of Zurich. “These social subpopulations have different survival and reproductive rates, so some might have greater competitive abilities than others, like being able to dominate the better-quality food, or there might be cultural differences such as having better strategies for protecting their calves from predators.”
Each giraffe social community exhibited different social characteristics, like how strong the relationships were among the community members. There was also a gradient in environmental characteristics in which the giraffe communities lived: the Tarangire region of northern Tanzania where the study occurred includes two national parks, a livestock and ecotourism ranch, and unprotected lands inhabited by traditional cattle ranchers, as well as several densely populated towns surrounded by agricultural lands. The scientists wondered how the environmental or social conditions experienced by the giraffes might influence their survival and reproduction. “Survival and reproduction together determine whether a wildlife population (or subpopulation like a specific girl gang) increases or decreases and is therefore absolutely critical for conservation,” said Lee.
The team calculated the survival rates of more than 1,400 adult females and calves, and the annual number of calves per female, and examined if there were differences among the social communities. They then investigated if the differences were explained by social factors like the strength of relationships, or by features of the environment, such as how close to people the giraffes roamed, the fertility of the soils, or the kind of vegetation in their ranges.
Giraffe calf survival was higher in social communities that had less area of dense bushlands in their ranges, possibly because lions prefer to hunt in such thickets where they can stalk their prey unseen. “We also found that calf survival and reproductive rates were higher in the social communities that spent more time outside of the national parks,” said Bond, probably also because there are fewer natural predators like lions and hyenas near where people live. Some areas outside the parks also had more fertile volcanic soils and therefore possibly more nutritious food than on other soil types.
“The good news for conservation is that giraffes can survive and raise their offspring in areas close to people,” Lee pointed out. “We can help giraffes to thrive by giving them enough living space in the savanna—both inside and outside of national parks—and by taking care not to disturb them and disrupt their social relationships.”
Wild Nature Institute celebrated the international day of forests by planting trees at Eunoto primary school, at Mungere village. A total of 150 native trees were planted with the help of students. Each student dug a hole and prepared organic manure from cow droppings and did the planting and watering themselves. Most of the students are coming from Maasai pastoralist communities. The area has plenty of water with a lot of birds and other wildlife from Lake Manyara and Mto wa Mbu.
All trees were planted successfully, thanks to kids who were learning quickly and eager to do the planting on their own. The school administration promised to look after trees and see them grow healthy.
We were joined by village officers and ward forest officers in the event, who were thankful to Wild Nature Institute for doing this for their village
Wild Nature Institute donated 150 of our Celebrating Africa's Giants bi-lingual (Kiswahili and English) children's books to 25 primary school libraries in Kenya, in partnership with Books Are Power, Inc.
These libraries together serve more than 7,000 Kenyan primary school children per year.
We are excited to share some photos of Kenyan children enjoying Our Elephant Neighbours, Juma the Giraffe, and Helping Brother Rhinoceros. These storybooks help make learning about African wildlife fun and accessible, while teaching language skills with the story side-by-side in English and Kiswahili.
Giraffes that group with others live longer
ZÜRICH - A 5-year study of more than 500 adult female giraffes in Tanzania found that individuals that grouped with more other females had higher survival. An international research team led by Dr. Monica Bond, research associate at University of Zurich and Wild Nature Institute Principal Scientist, published their results this week in Proceedings of the Royal Society B. The study examined the relative effects of sociability, the natural environment, and human factors on survival of this charismatic megaherbivore, and showed giraffes that are observed in larger groups have higher survival, and that social factors outweighed human and environmental factors.
“Giraffe group formations are dynamic and change throughout the day, but adult females maintain many specific friendships over the long term,” said Bond. “Grouping with more females, called gregariousness, is correlated with better survival of female giraffes, even as group membership is frequently changing. This aspect of giraffe sociability is even more important than attributes of their non-social environment such as vegetation and nearness to human settlements.”
Bond’s team studied wild free-ranging giraffes over multiple years and documented their social behaviors using network analysis algorithms similar to those used by big data social media platforms. The friends network of giraffes uses mathematics to describe their social patterns, and the team found giraffes are surprisingly similar to people and other primates in their social habits, where greater social connectedness matters. Humans with extensive social networks can take advantage of many more opportunities relative to someone with a more restricted network. Likewise, chimpanzees and gorillas live in communities where ties between many individuals can be advantageous because they facilitate movements among groups and with familiar individuals, which facilitates flexibility of feeding strategies. It seems to be beneficial for female giraffes to connect with a greater number of others and develop a sense of larger community but not a strong sense of exclusive subgroup affiliation.
Why might living in larger groups bring survival benefits for giraffes? Grouping behavior may increase adult survival for species where adults themselves are prey, as larger groups can better detect predators or deflect predation from themselves. But adult female giraffes are far less vulnerable to natural predation than are their calves. Aside from poaching, the main culprits of adult female giraffe mortality are likely to be disease, stress, or malnutrition, all of which are interconnected stressors.
“Social relationships can improve foraging efficiency, and help manage intraspecific competition, predation, disease risk, and psychosocial stress,” noted Dr. Barbara König of the University of Zurich and senior author of the study. Female giraffes may be seeking out and joining with an optimal number of other females in order to share and obtain information about the highest-quality food sources. Other benefits to living in larger groups might be lowering stress levels by reducing harassment from males, cooperating in caring for young, or simply experiencing physiological benefits by being around familiar females.
Features of a female giraffe’s non-social environment were less correlated with survival than her gregariousness, but the study also found that females living closer to towns had lower survival, possibly due to poaching that originates in these areas. Previous research in our study population revealed differences in giraffe behaviors near towns. Closer to towns, adult female home ranges were larger in size and female groups with calves avoided towns.
For the past decade the international team has been conducting the largest study of a giraffe population in the world. The vast scale of their study area in the Tarangire region of Tanzania spans more than a thousand square kilometers and includes multiple social communities, each with about 60 to 90 adult female members. Thus, the study was able to disentangle individual from community level influences on survival. The study is also unique in combining social network analysis and modeling of vital rates such as survival in a sample of hundreds of individuals.
Wild Nature Institute thanks our wonderful financial supporters who fund our giraffe field work, including Sacramento Zoo, Columbus Zoo and Aquarium, Tulsa Zoo, Tierpark Berlin and Zoo Berlin, Cincinnati Zoo and Botanical Garden, Zoo Miami, GreaterGood.org Project Peril, and Save the Giraffes.
We wish a very happy birthday to the brilliant, beautiful, and indefatigable Dr. Anne Innis Dagg, the first person to scientifically study giraffe behavior in the wild. She is an inspiration to giraffologists everywhere!
Wild Nature Institute's giraffe research makes the cover of the Journal of Animal Ecology!
Cover image: Female Masai giraffes that live closer to human settlements have weaker and more exclusive relationships with other members of their social communities compared with those living deep within protected areas. See page 212‐221. Photo by Derek Lee.
Wild Nature Institute is pleased to share our 2020 Annual Report. Despite the challenges of the pandemic, we successfully continued and expanded our giraffe conservation science and education in Tanzania thanks to donations from our committed supporters, and thanks to our fantastic Tanzanian staff who rose to the occasion and did great work. We hope you enjoy reading about what we have all accomplished this year.
This week, as some of the largest wildfires in decades continue to burn across U.S. western states, a group of pro-logging scientists and activists reignited the debate about spotted owls and wildfires by publishing a comment article critical of a 2018 synthesis of all scientific evidence on the topic. Federal and state authorities are pushing plans to increase government-subsidized logging in national forests, claiming such logging would protect spotted owls from wildfire.
Derek Lee, associate research professor at Pennsylvania State University and author of the 2018 synthesis said, "spotted owls are usually not affected by wildfire, but there are also significant benefits to reproduction from high-severity fire. I believe money intended for logging national forests would be better spent hardening homes and other human structures to protect lives and property against wildfire." There are limited resources available to protect homes and communities from wildfire, and logging backcountry forested lands such as in owl habitats has no impact on community safety, so Lee argues that forest fire mitigation resources should be focused on home fire resistance and protection. The only proven way to protect homes and lives from wildfires is to create fire-safe communities, improve warning systems, and provide evacuation assistance, measures contained in the Wildfire Defense Act introduced by Sen. Kamala Harris (D-Calif.).
Gavin Jones, U.S. Forest Service Researcher and lead author of the comment affirmed Lee's observation saying, "Severe fire has not resulted in range-wide spotted owl population declines, and fire has not been an overriding driver of recently observed long-term spotted owl population declines." However, the Jones-led group of pro-logging scientists and activists also suggested several analytical changes to the 2018 synthesis, and speculated such changes might affect the results and conclusions. Published alongside the comment article was a reply by Lee that reanalyzed all the data according to the Jones group's suggestions and found none of the group's assertions were accurate.
According to Lee, forest fire provides significant benefits to owl populations. Lee's analysis indicated significant positive effects in recruitment, reproduction, and foraging habitat selection in burned forest, with reproduction increasing as the amount of high-severity fire increased. Lee explained, "The absence of big negative effects of fire on spotted owls was not surprising because this species has been living with forest fire for thousands of years. The positive effects of forest fires on spotted owls indicate wildfires, including so-called mega-fires, are within the natural range of variability for these forests. The fact that spotted owls have adapted to these types of fires over evolutionary time shows that they have seen this before and learned to take advantage of it. The Jones group is cherry-picking evidence to support damaging logging in the name of fire-risk reduction rather than following the evidence and advocating for more fire to enhance spotted owl habitat." Additionally, burned forests with large patches of high-severity fire are useful habitat that provide significant benefits to many other native species.
Lee's findings run contrary to current perceptions and forest management projects for the spotted owl, which counterfactually insist fire is a threat and that unproven logging treatments are needed. The USDA Forest Service budget is largely devoted to administering and facilitating logging projects, so there are financial incentives for this agency to promote logging on public lands. Lee added, "Thinning and logging intended to reduce fire severity in spotted owl habitat will harm the owl and diverts resources that should be used to save human lives and property. Chainsaws felling trees in our forests' backcountry will not save human lives, only hardening human structures against ignition will save people. In addition to spotted owls, there are many other native plants and animals that thrive in forests burned by high-severity fire. Wildfires create valuable natural habitats that should be protected from damaging management activities like post-fire logging."
Spotted owls occur in western U.S. forests and are one of the best-studied birds in the world. The species is strongly associated with mature and old-growth conifer and mixed-conifer–hardwood forests with thick overhead canopy and many large live and dead trees and fallen logs. Its association with older forests has made the spotted owl an important species for public lands management aimed at preserving the last remaining fragments of our old-growth forests. Research on spotted owls in fire-affected landscapes did not begin until the early 2000s. Much of what scientists previously understood about habitat associations of spotted owls was from studies in forests that had generally not experienced recent fire, and where non-suitable vegetation was a result of logging.
Western forest fires typically burn as mixed-severity fires with each fire resulting in a mosaic of different vegetation burn severities, including substantial patches of high-severity fire. Anywhere from 5% to 70% of the fire area typically burns as high-severity fire that kills most or all of the dominant vegetation in a stand and creates extremely biodiverse snag forests, where standing dead trees, fallen logs, shrubs, tree seedlings, and herbaceous plants contribute to forest structure. Post-fire vegetation processes then proceed according to the pre-fire vegetation, local wildfire processes, seeds from outside the disturbance, and the conditions at the site.
By reviewing past extinction patterns, a new study suggest that herbivores may be at the highest risk of extinction. A team of researchers from the US and UK studied more than 44,000 living and extinct species, specifically looking at their diets. Trisha Atwood, lead author of the study published in Science Advances, said “[we built] a dataset so we could determine which trophic level is at highest risk for extinction.” Many researchers had previously assumed predators had the highest extinction rates because of their extensive home ranges and slow population growth rates, but that wasn’t the case. The team found that herbivores consistently have had the highest risks of extinction, including from the present day to the late Pleistocene. This observed elevated extinction risk for herbivores is ecologically consequential, given the important roles that herbivores are known to play in controlling ecosystem function.
Wild Nature Institute works to protect herbivores like hoofed mammals and elephants in northern Tanzania through the TUNGO program.
Science News and Updates From the Field from Wild Nature Institute.
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