Masai giraffes are nearing critically endangered status

Eastern Africa’s Masai giraffes are walking on the thin ice of extinction, according to a compelling new study from Penn State. Far more imperiled than initially estimated, these towering creatures face geographic barriers that have limited their gene flow for over a millennium.

The researchers made the stunning discovery that the Great Rift Valley, a significant geological feature, has split the Masai giraffe population into two distinct factions. These groups have not interbred or traded genetic material for thousands of years, creating two separate gene pools isolated for an impressively long period.

Given this newfound knowledge, scientists are urging separate but synchronized conservation efforts to protect each unique giraffe population. In a world where giraffe numbers have plummeted over the last three decades, the situation is more desperate than ever. With less than 100,000 of these magnificent creatures left worldwide, every conservation action counts.

More than half of the giraffe population has vanished

The Masai giraffe, native to Tanzania and southern Kenya, has suffered a harrowing 50 percent population decrease due to illegal hunting and habitat encroachment. These factors have pushed this species, recognized as endangered by the International Union for Conservation of Nature (IUCN), towards the brink, leaving only about 35,000 individuals in the wild.

Douglas Cavener, the Dorothy Foehr Huck and J. Lloyd Huck Distinguished Chair in Evolutionary Genetics and professor of Biology at Penn State, attributes this plight in part to human population surge in East Africa. Over the past 30 years, rapid human expansion has fragmented the giraffes’ habitat.

Professor Cavener further explains the role of the Great Rift Valley, a formidable natural boundary that bisects East Africa, impeding wildlife migration. This obstacle spurred researchers to examine the genomes of 100 Masai giraffes, trying to uncover whether populations on either side of the rift have interbred recently, a question with profound implications for conservation.

Giraffes, unfortunately, are not adept climbers, further complicating matters. Using high-resolution satellite data, the experts found only two locations where the slopes of the rift were gentle enough for giraffes to traverse. Yet, there’s no evidence of these long-necked mammals ever taking such a route.

How the study was conducted

To delve into the genetic history of the animals, scientists sequenced their nuclear and mitochondrial genomes. Nuclear genome comprises genetic material inherited from both parents, while mitochondrial genome carries only maternal lineage. The study findings are published in the journal Ecology and Evolution.

“Interbreeding among different populations results in the exchange of genetic information – often called gene flow – and is generally considered to be beneficial because it can improve overall genetic diversity and help buffer small populations against disease and other threats,” said Lan Wu-Cavener, assistant research professor of biology and a member of the research team. 

“To understand potential gene flow across the rift, we sequenced the more than 2 billion base pairs that make up entire nuclear genome as well as the more than 16,000 base pairs that make up the entire mitochondrial genome. This complex data presented a variety of computational and data storage challenges for our small team, but using the entire genome instead of a small portion allowed us to definitively investigate the extent of gene flow among these populations.”

What the researchers learned

After identifying several gene blocks inherited together, or haplotypes, in the mitochondrial genome, researchers conducted a network analysis. This investigation revealed that giraffes from either side of the rift had no overlapping haplotypes, suggesting no female migration for breeding in the past 250,000 to 300,000 years.

Cavener notes that this discovery defied the team’s initial hypotheses. Initially, they believed one population was founded, with some individuals crossing the rift to create a second group. But the study findings indicate that the two populations were established independently over 200,000 years ago.

Analysis of the nuclear genome suggests male-mediated gene flow might have occurred as recently as a thousand years ago. To gain better insight, researchers plan to study additional samples from both populations.

More research is needed to develop a plan

Cavener emphasizes that the study’s findings highlight that the giraffe populations on either side of the rift are genetically distinct. This fact carries a two-fold implication; each population exhibits less genetic diversity than if they were a unified group, and the prospects of these giraffes naturally crossing over the rift are extremely slim. 

Translocating these colossal creatures isn’t practical either. Consequently, the Masai giraffes are at a higher risk of extinction than previously believed.

Cavener passionately advocates for more focused, independent, yet coordinated conservation efforts for each population. With a plea to the Tanzanian and Kenyan governments, he stresses the need for amplified protection for these giraffes and their habitats, particularly in the face of increased poaching in the region.

Disturbing indicators of inbreeding

The researchers also unearthed worrisome indicators of inbreeding on both sides of the rift, a phenomenon that saps the genetic diversity and overall fitness of the population. Future research plans include further exploration of Masai giraffe populations on both sides of the rift, with a special focus on the particularly isolated ones. The aim is to comprehend the risks these animals face due to inbreeding better.

Moreover, the scientists plan to examine giraffe movements between groups on the east side of the rift, where the habitat is notably fragmented. This endeavor seeks to prioritize conservation efforts effectively to maintain connectivity between these groups.

Cavener further expressed a desire to clarify parent-child and sibling relationships in Masai giraffes using genetics. He acknowledges significant knowledge gaps in giraffe mating behavior, such as the number of successful male breeders in a local population over several years. These questions bear great significance for estimating the actual breeding population and will continue to guide efforts to protect and conserve these majestic creatures.

The research team also included first author George Lohay, postdoctoral scholar, Derek Lee, Associate Research Professor of Biology, Monica Bond, academic affiliate in biology, David Pearce, an undergraduate student, and Xiaoyi Hou, a graduate student. The Penn State Department of Biology, the Eberly College of Science, the Huck Institutes of the Life Sciences, and the Wild Nature Institute supported this groundbreaking work.

More about giraffes

Giraffes are one of the most fascinating and easily recognizable creatures in the animal kingdom, thanks to their long necks and distinctive spotted patterns. Let’s dive into what makes these animals unique:

Species and classification

Giraffes belong to the family Giraffidae, which only has two extant members: the giraffe and the okapi. The giraffe species (Giraffa camelopardalis) has several subspecies, distinguished by their different geographic habitats and variations in coat patterns. These subspecies include the Masai, Reticulated, Rothschild’s, South African, and others. However, recent genetic research has suggested that these subspecies could potentially be separate species.

Physical attributes 

Giraffes are the tallest terrestrial animals, standing up to 5.5 meters (18 feet) tall. Their necks can reach lengths of up to 2.4 meters (8 feet), and they have a small hump on their backs. Each giraffe’s coat pattern is unique, much like human fingerprints.

Neck and legs

Despite their remarkable length, a giraffe’s neck contains only seven vertebrae – the same number found in human necks. The difference is that each vertebra can be up to 10 inches long. Giraffes have long legs, which are approximately the same length as their necks. Their front legs are slightly longer than their back legs.

Horns

Both male and female giraffes have a pair of horn-like structures on their heads known as ossicones. In males, these ossicones can be used in combat, while in females, they are smaller and have tufts of hair on top.

Diet

Giraffes are herbivores, primarily feeding on the leaves and shoots of acacia trees, which are rich in nutrients and water. Their long necks and a specialized tongue, which can reach up to 45 centimeters (18 inches) in length, allow them to reach foliage that most other herbivores cannot access.

Social structure

Giraffes typically live in loose social groups that can vary in size. These groups often change composition, although they usually consist of a group of females and their offspring, with adult males typically living either alone or in small groups.

Reproduction

Female giraffes have a gestation period of about 15 months. They usually give birth to a single calf, although twins are not unheard of. Newborn giraffes are about 2 meters (6 feet) tall and can stand and walk within a few hours of birth.

Lifespan and predation

Giraffes have a lifespan of up to 25 years in the wild, though this can be extended in captivity. Their height gives them a good vantage point to spot predators from a distance. Predators include lions and hyenas, with young giraffes being the most susceptible.

Conservation status 

Many giraffe populations are threatened due to habitat loss, illegal hunting, disease, and climate change. The International Union for Conservation of Nature (IUCN) lists some subspecies as “Vulnerable” or “Endangered.”

Behavior and communication

Giraffes are generally calm animals. They communicate using body movements and postures, and recent research suggests they also communicate in sounds that are below the range of human hearing.

Sleep patterns

Giraffes have one of the shortest sleep requirements of any mammal. They sleep for only a few minutes at a time, adding up to about 30 minutes of sleep per day. When they do sleep, it’s usually in short bursts, often standing up.

Drinking habits 

Given their height, drinking water from a lake or pond is an awkward, vulnerable act for a giraffe. They have to awkwardly splay their front legs or bend their knees to reach down, which can make them susceptible to predators. Luckily, the leaves they eat contain a lot of water, so they don’t need to drink very often.

Running speed

Despite their ungainly appearance, giraffes can run surprisingly fast – up to 35 miles per hour (56 kilometers per hour) over short distances. Their gallop is unique among mammals, as they move both right legs forward and then both left legs, rather than alternating.

Heart and blood pressure 

Due to their height, giraffes have developed unique cardiovascular systems. Their hearts, which can weigh up to 25 pounds (11 kilograms) and are about 2 feet (0.6 meters) long, have to pump blood against gravity to reach the brain. As a result, giraffes have the highest blood pressure among land mammals. Their blood vessels, particularly in the lower legs, are adapted to withstand high pressure.

Predator defense

Adult giraffes are capable of delivering powerful kicks, especially when threatened by predators like lions. These kicks can be fatal for the predators.

Conservation efforts 

In response to declining populations, several conservation efforts are being undertaken worldwide. These include tracking and monitoring giraffe movements, habitat management, reducing human-giraffe conflicts, and working towards stronger laws and regulations to protect them.

Cultural significance

Giraffes have long held cultural significance for humans and often feature in works of art, literature, and popular culture. They’ve been depicted in rock and cave paintings from prehistoric times. In many African cultures, giraffes symbolize grace, peace, individuality, and protection.

Each of these points underscores the giraffe’s unique biology and the important role it plays in our world’s biodiversity. The conservation of these magnificent creatures and their habitats is critical to maintaining the rich diversity of our planet’s ecosystems.

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