wildlife conservation

Rising Rainfall, not Temperatures, Threaten Giraffe Survival

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Giraffes in the East African savannas adapt well to warmer temperatures. However, they are threatened by increasingly heavy rainfall.

 

Climate change is expected to cause widespread declines in wildlife populations worldwide. Climate anomalies interacting with human pressures can place additional stress on already declining populations, but little is known about the interactions between climate and anthropogenic effects on large African herbivore species despite the growing importance of these pressures. Giraffes are endangered megaherbivores, but the combined climate and human effects on the survival rates not only of giraffes, but of any large African herbivore species, had not been studied. We concluded a decade-long study – the largest to date – of a giraffe population in the Tarangire region of Tanzania. The study area spanned more than a thousand square kilometers, including areas inside and outside protected areas. Contrary to expectations, higher temperatures were found to positively affect adult giraffe survival, while rainier wet seasons negatively impacted adult and calf survival. The results were published in the journal Biodiversity and Conservation.

 

First exploration into the effects of climate variation on giraffe survival

Our research team quantified the effects of local anomalies of temperature, rainfall, and vegetation greenness on the probability of survival of the giraffes. We also explored whether climate had a greater effect on giraffes that were also experiencing human impacts at the edges of the protected reserves.

Studying the effects of climate and human pressures on a long-lived and slow-breeding animal like a giraffe requires monitoring their populations over a lengthy time period and over a large area, enough to capture both climate variation and any immediate or delayed effects on survival. We obtained nearly two decades of data on local rainfall, vegetation greenness, and temperature during Tanzania’s short rains, long rains, and dry season, and then followed the fates of 2,385 individually recognized giraffes of all ages and sexes over the final 8 years of the two-decade period.

Masai giraffes in a heavy downpour, Tanzania. Photo credit: Derek Lee

Surprising effects of temperature on giraffe survival

We had predicted that higher temperatures would hurt adult giraffes because their very large body size might make them overheat, but higher temperatures positively affected adult giraffe survival. This is because the giraffe has several physical features that help it to keep cool, like long necks and legs for evaporative heat loss, specialized nasal cavities, an intricate network of arteries that supply blood to the brain, and they radiate heat through their spot patches. However, temperatures during our study period may not have exceeded the tolerable thermal range for giraffes, and an extreme heat wave in the future might reveal a threshold above which these massive animals might be harmed. So we will continue to monitor this population.

 

Heavy rains may increase parasites while reducing nutritional value of vegetation

Survival of giraffe adults and calves was reduced during rainier wet seasons, which we attributed to a possible increase in parasites and disease. A previous study in the Tarangire region showed giraffe gastrointestinal parasite intensity was higher during the rainy seasons than the dry season, and heavy flooding has caused severe outbreaks of diseases known to cause mortality in giraffes, such as Rift Valley Fever Virus and anthrax. The current study also found higher vegetation greenness reduced adult giraffe survival, potentially because faster leaf growth reduces nutrient quality in giraffe food.

 

Human pressure place additional stress on already declining populations

Climate effects were exacerbated by the giraffe’s proximity to the edge of protected reserves, but not during every season. Our findings indicate that giraffes living near the peripheries of the protected areas are most vulnerable during heavy short rains. These conditions likely heighten disease risks associated with livestock, and muddy terrain hampers anti-poaching patrols, leading to increased threats to giraffe survival.

Climate anomaly effects on seasonal survival of adult Masai giraffes in Tarangire Ecosystem, Tanzania 2012‒2019. MeanDistPA is mean distance from the edge of the protected area (km). M = male; F = female.
Rainfall anomaly effects on Masai giraffe juvenile seasonal survival from the Tarangire Ecosystem, Tanzania 2012‒2019. PA distance is mean distance from the edge of the protected area (km). M = male; F = female, and U = unknown sex.

We concluded that projected climate changes in East Africa, including heavier rainfall during the short rains, will likely threaten persistence of giraffes in one of Earth’s most important landscapes for large mammals, indicating the need for effective land-use planning and anti-poaching to improve giraffes’ resilience to the coming changes.

The paper is available for download at https://doi.org/10.1007/s10531-023-02645-4

Climate change threats to a short-lived primate

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Climate change changes temperature and rainfall patterns, particularly in tropical environments, resulting in consequences for the persistence of wildlife populations. However, the complexities of the effects of changing temperature and rainfall on tropical mammals is not well studied. Together with our colleagues, we studied the demography of the gray mouse lemur in western Madagascar using data collected by the German Primate Center between 1994 and 2020. Climate trends in the lemur’s environment show declining rainfall over the wet season and increasing temperatures in the dry season. These climate trends, we found, led to decreased survival rates as well as increased reproductive rates. The competing demographic trends have prevented population collapse, but have destabilized the population by further speeding up their life cycle which was already one of the fastest among primates. Population projections into the next five decades suggest that when recently observed temperature and rainfall conditions persist, the population size of lemurs may continue to fluctuate, putting the population at increased risk of extinction. Our results show how, even though short-lived mammal species with high reproductive rates are expected to rapidly adapt to changes in their environment, such species can still face threats of extinction from climate change.

Link to the article:  Ozgul A, Fichtel C, Paniw M, Kappeler PM (2023) Destabilising effect of climate change on the persistence of a short-lived primate. Proceedings of the National Academy of Sciences USA

The walk of life: African wild dog dispersal and what it means for management and conservation

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The African wild dog is Africa’s most endangered large carnivore and is listed as endangered in the IUCN Red List. Less than 6’000 free-ranging individuals survive in the wild and the species has been given very high conservation priority.

The African wild dog, like few other territorial land species, is characterized by the need for vast semi-pristine and undisturbed areas. This peculiarity makes it particularly vulnerable to habitat loss, deterioration, and fragmentation. This highlights the importance of landscape connectivity between subpopulations in and around protected areas.

A deeper understanding of where and how resident packs and dispersing individuals move, and the demographic consequences of dispersal, is therefore important for the management and conservation of the species over larger landscapes such as the Kavango-Zambesi Transfrontier Conservation Area (KAZA/TFCA).

On Christmas day 2018, we were able to observe the first high-resolution trans boundary dispersal from Botswana’s Okavango Delta to Zimbabwe’s Hwange National Park. This journey highlights the central role of Botswana in the KAZA/TFCA trans boundary conservation effort, as well as the role of the African wild dog as a flagship species.

On 16th December 2018, four sisters dispersed from their pack resident just outside Moremi Gamer Reserve in Botswana. The pack is part of a long term study and is regularly followed by our collaborators on site, the Botswana Predator Conservation Trust. This dispersing coalition is somehow unusual, as it is composed of females born to the same mother but in three different litters (in three consecutive years). The coalition dispersed in an almost straight line moving east and crossed the Zimbabwean border after covering an astonishing 280 km. They continued and covered additional 100 km within Hwange National Park, totalling 360 km in only nine days! Thanks to a collaboration with the Zimbabwean-based Painted Dog Conservation Program, we were able to confirm that all four females are still alive and in good conditions. As they seem to have slowed down a little, the daily covered distance much decreased in the past few days, we expect them to soon associate with unrelated males. The formation of a new pack and the settlement in a new territory is the ultimate goal of dispersal, as successful dispersal allow gene flow between subpopulations and for the recolonisation of empty areas.

We will be able to continue monitoring this dispersal event, thanks to the Satellite technology in the radio collar and to the support of the folks at Painted Dog Conservation in Zimbabwe.  Stay tune for more updates on these girls and on future dispersers.

Trans boundary dispersal event from Botswana’s Okavango Delta to Zimbabwe’s Hwange National Park. The blue line represents the dispersal trajectory, the yellow line the international boundaries. The red square represents the last recorded location.

On the Trail of Giants: Population Ecology of Giraffes in Tanzania

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“Kuna twiga pale,” I say in Swahili to our driver Meshak. There are giraffes over there. My partner Dr. Derek Lee and I stand side-by-side in the back of our Land Cruiser, its top opened, and peer through our binoculars at a herd of Masai giraffes (Giraffa camelopardalis tippelskirchi) feeding on umbrella-shaped Acacia tortillis trees several hundred meters away. We are deep in the heart of Tarangire National Park in northern Tanzania, East Africa. “I see at least 12 giraffes,” Derek says. “Let’s head over there.” As our vehicle bumps across the savanna towards the herd, some individuals continue eating and milling around, while some lift their heads and watch our approach, serenely chewing their wads of cud. As long as we advance slowly and do not drive directly towards them, they are unconcerned.

A group of young male giraffes in Tarangire National Park

We carefully scan the ground for aardvark holes and logs hidden in the grass as we proceed forward. The closer we get to the giraffes, it strikes me how absurdly tall and oddly shaped, yet wonderfully elegant these majestic creatures are, the world’s tallest of animals. When we are about 70 meters from the closest giraffe, we swing the vehicle around to see her right side. Derek photographs her while I measure her exact distance away from the camera using a laser rangefinder, so later we can use photogrammetry to calculate her height. I record the photograph number, her distance from camera, and her sex and age class in our field notebook. Moving on to the other giraffes, we weave in and out of the trees and bushes, constantly adjusting our angle to get photos perpendicular to the animal. If we witness a nursing calf, we make a note connecting the cow-calf pair. We also record anything unusual such as signs of disease or injury. After everyone has been photographed, we mark a GPS location in the approximate center of the group, make a final count of all the giraffes, and follow our original tracks back to the road. As we drive off, the giraffes stare after us with their big, long-lashed eyes, chewing intermittently, but otherwise completely unfazed as we depart with more data points in our growing set of thousands of photographic giraffe ‘captures.’

A male giraffe in Tarangire National Park

Derek and I are implementing the world’s largest individual-based demographic study of giraffes in terms of sample size and area sampled. We conduct six surveys per year towards the end of each of Tanzania’s three precipitation seasons, with every survey lasting about 10 days. We are investigating births, deaths and movements of giraffes in the Tarangire ecosystem—a region undergoing rapid anthropogenic land-use changes—to understand where they are doing well and why, and using that information to conserve declining giraffe populations. For my PhD in the Program Ecology at the University of Zürich, I will be using our photographic capture-recapture data to study giraffe natal dispersal patterns and to quantify the fitness consequences of their social dynamics. I am part of both the ‘Population Ecology’ and the ‘Cooperation and Social Structuring in Mammals’ research groups.

Monica Bond holds a giraffe skull
Dr. Derek Lee photographs a giraffe for identification in Tarangire National Park

Despite being an African icon and one of the planet’s last mega-herbivore species, giraffes remain understudied in the wild. In part, this is because giraffes were not intensively hunted until recently in some areas: they don’t produce tusks or horns that are coveted as trophies or medicine and they are not an aggressive species. Sadly, however, giraffes are becoming increasingly endangered throughout their range in sub-Saharan Africa due to conversion of savanna woodland habitat to agriculture, deforestation for charcoal, and bushmeat poaching.

A giraffe browses on Acacia

Giraffe numbers have plummeted across Africa by an estimated 40 percent in the last few decades, to the point where they now number far fewer than African elephants. The IUCN recently upgraded the species Giraffa camelopardis to “vulnerable” on the Red List (while scientists are debating the number of species, all giraffes are currently still considered to be one species). Most giraffe populations are now largely restricted to lands in and around national parks. Predation by lions and hyenas also can negatively affect giraffe survival—a natural phenomenon that becomes a problem as wildlife are squeezed into small protected areas.

Lions prey upon giraffe calves and sometimes adults

After decades of little research on the wild giraffes, scientists are showing renewed interest in these gentle giants because of their declining numbers. Derek and I began photographing individual giraffes in 2011 to build a database of demographic information on giraffes across the Tarangire ecosystem. This region, which contains two national parks and a large private ranch embedded within a matrix of village lands, is known for its extraordinary diversity and abundance of large mammals including giraffes, elephants, zebras, antelopes, lions, and leopards, but these magnificent animals exist in a landscape undergoing rapid changes.

Drinking can be awkward for a giraffe

The Tarangire ecosystem is second in giraffe density only to the nearby world-famous Serengeti ecosystem, but unlike the Serengeti, land in Tarangire is largely unprotected. Since the 1940s, human population and agricultural expansion in Tarangire have increased fivefold, causing substantial habitat loss and fragmentation. Bushmeat poaching is also a serious problem—recent research suggests that each year poachers kill about 90 giraffes in just one small part of the Tarangire ecosystem. Giraffes are hunted at night, dazed by spotlights or confused by loud horns and killed with machetes or spears; giraffes are also targeted with wire neck snares set high in the tree canopy.

Monica Bond speaks with local Masai tribal members

We study wild giraffes using two technologies, digital photography and pattern-recognition software, to identify and track individuals by their coat patterns. Every giraffe has unique and unchanging spot patterns, much like the human fingerprint. These patterns enable us to identify and monitor individual giraffes with the aid of a computer algorithm that matches the thousands of photographs we collect during our surveys. We can determine where and when we last saw the animal, whether a female was pregnant or nursing, and who else was in the herd. Demographic studies of uniquely patterned species using the non-invasive photographic method have grown in popularity as digital cameras and pattern-recognition software have improved. These technologies allow us to compile demographic data on thousands of giraffes—sample sizes unheard of in the days before computers. The method is also much less expensive than physical captures for marking of large mammals, and is entirely non-invasive and non-traumatic. Other recent demographic studies using pattern-recognition software with digital photographs have been conducted on wild dogs, wildebeests, and even toads (my UZH colleagues Sam Cruickshanck and Benedict Schmidt just published a study on yellow-bellied toads in Switzerland using the same pattern-recognition software that we use).

Wild ID pattern-matching computer software

To date we have identified and are monitoring over 3,100 individual giraffes. We aim to understand factors affecting survival and reproduction in landscapes subjected to different human uses, including parks and village lands, and also to identify important calving grounds and critical movement pathways. My PhD research will help ascertain how human and natural factors influence sociality and fitness, and how these mega-herbivores move around the ecosystem, which will provide insights into what may be the most effective conservation measures. The ultimate goal is to enable healthy populations of giraffes to continue roaming across this ecosystem as they have for eons, fulfilling their important ecological functions and delighting humans for generations to come. The Masai Giraffe Conservation Demography Project is being conducted by the Wild Nature Institute. Visit their website to learn more.

Giraffe calves in Lake Manyara National Park