Giraffe species can interbreed in captivity. In the wild, the ranges of Nubian, reticulated and Masai giraffes meet in Kenya, with no obvious natural barrier along some of their boundaries. If animals from these neighbouring groups regularly bred together, their descendants could gradually blur the genetic differences between them. So how separate are they where they have opportunities to meet?
Raphael T. F. Coimbra and colleagues addressed that question in a 2023 study in BMC Biology. They found that the three groups remained strongly distinct across their genomes, the complete sets of DNA they inherit. Yet some reticulated giraffes carried ancestry from Nubian giraffes, which belong to the northern giraffe species. Past interbreeding had left a legacy without dissolving the broader differences between species.
That is a useful distinction for conservation. A population can share some ancestors with its neighbours and still represent an evolutionary lineage with its own inheritance to protect. The team's evidence helps explain why northern, reticulated and Masai giraffes deserve separate attention when assessing their losses or planning conservation movements.
Looking where giraffe ranges meet
The Laikipia Plateau was an especially informative place to look. Nubian and reticulated giraffes were suspected to have interbred there, partly because some animals had intermediate coat patterns. DNA offered a way to investigate ancestry directly. A coat shows a small part of an animal's biology; a genome contains inherited variants spread across thousands of genes and the DNA between them.
The Giraffe Conservation Foundation, Kenya Wildlife Service and local partners obtained tissue samples across Kenya. Coimbra's team generated 113 new genomes and combined them with 15 published genomes from East Africa, including animals outside the suspected contact zones. That wider comparison helped distinguish a local mixture from the broader differences between the groups.
Researchers compared positions where giraffes carry different DNA letters. Close relatives were excluded from the population analysis so that a heavily sampled family would not dominate the pattern. When the team examined these variants together, Nubian, reticulated and Masai giraffes formed distinct groups. A family tree reconstructed from DNA across the cell nucleus also supported their separation.
The important result was the combination: strong differences persisted across the genome, even in a study deliberately looking where interbreeding seemed most plausible. The exceptional animals could then be understood against that background.
One giraffe carries two parts of the story
A reticulated giraffe identified as GF292 had a particularly revealing genome. Most of its ancestry was reticulated, but a substantial component was Nubian. Its mitochondrial DNA also belonged to the Nubian lineage.
The two kinds of DNA tell different parts of a family history. Most DNA sits in the cell nucleus and comes from both parents. Mitochondrial DNA is a much smaller genome passed from a mother to her offspring. An animal can therefore inherit a mixture of nuclear DNA while carrying a maternal lineage associated with one ancestral population.
GF292 also fell between the northern and reticulated groups in the nuclear family tree. The authors interpreted it as a possible recent hybrid, or more likely a backcross: the descendant of a hybrid breeding with one of the parental populations. For example, descendants breeding repeatedly into the reticulated population could inherit an increasingly reticulated nuclear genome while a Nubian mitochondrial lineage continued through mothers and daughters.
That is a reconstruction from DNA, rather than a known pedigree. Several parts of GF292's genome support mixed ancestry, but they do not identify its parents or date the original encounter. This animal makes the broader discovery tangible: occasional interbreeding can leave a recognisable inheritance inside a population that remains distinct overall.
Thirteen ancestry signals do not all mean the same thing
To look for mixed ancestry, the researchers used models that describe each genome as a combination of genetic groups. A broad model might allow only the three main giraffe groups. A more detailed one can also represent differences between local populations within them.
That choice changed the picture in Laikipia. In the broad analyses, 13 reticulated giraffes showed a Nubian ancestry component. Once the model could recognise more local groups, most of those animals formed a Laikipia group of their own. Only two, GF292 and GF295, consistently retained the Nubian signal.
Why does this happen? A local population can have a distinctive history that a broad model has no separate category for. The model may describe that population as a mixture of the larger groups instead. Giving it room to represent local differences can change how much ancestry it assigns to each source. The 13 animals therefore cannot simply be counted as 13 recent hybrids.
Other comparisons nevertheless supported a history of interbreeding in Laikipia. The team looked for DNA variants shared between Nubian and reticulated giraffes more often than a family tree with no later exchange would predict. Those analyses pointed mainly to ancestral exchange. Together, the findings suggest a regional legacy of older contact, with a stronger individual signal in a few giraffes.
Scientists call the lasting transfer of DNA through interbreeding and subsequent generations introgression. Once a variant has entered a population, descendants can keep passing it on. Its presence today does not require the two populations to be interbreeding today.
Is that exchange still happening?
The team also examined a much more recent window: roughly the last two generations. The estimated rates of exchange were low, but every uncertainty interval included zero. The analysis therefore could not distinguish rare recent exchange from none at all. That result fits limited mixing, while leaving GF292's exact family history unresolved.
Another finding showed why even a striking maternal lineage needs interpretation. Three Masai giraffes carried mitochondrial variants associated with reticulated giraffes. Ancient interbreeding is one possible explanation. Another is that variants already present in the population ancestral to both groups survived in their descendants. This is called incomplete lineage sorting.
The authors could not choose confidently between those explanations for the three animals. Comparing maternal DNA with DNA inherited from both parents is valuable because a single line of descent does not describe the whole animal's ancestry. Our taxonomy and genetics guide develops that distinction.
Different lineages need their own conservation attention
Coimbra and colleagues supplied genomic evidence for interbreeding that had previously been suspected from appearances, while showing how little it had altered the broad separation of these giraffes. The authors argue that conservation translocations should take those distinctions into account. Moving animals requires knowing which lineage a source and recipient population represent, as well as recognising local ancestry within them.
The finding also helps explain a long-running scientific debate. Alice Petzold and Alexandre Hassanin's 2020 analysis compared several ways of grouping giraffes using 21 nuclear introns, DNA sections within genes that do not code for proteins. Changes in assumptions produced support for different numbers of groups; their combined evidence favoured three species, including reticulated giraffes within the northern grouping. Coimbra's genome-wide evidence supported separating northern and reticulated giraffes even after examining their suspected contact zone. The disagreement shows why a model's number of groups alone cannot settle a species classification: the extent and history of exchange also matter.
Sam van Giessen and colleagues' 2026 study in South Sudan illustrates the importance of geography within those lineages. Adding previously little-studied Nubian giraffes revealed a regional group shared with Ethiopia. Some apparent mixtures between species also disappeared when the models allowed more groups. Both studies show how representing local population history can sharpen an ancestry interpretation. The South Sudan story explains why the genetic variety retained there matters for future generations.
What keeps neighbouring giraffes distinct?
The genomes establish a pattern more firmly than they explain the behaviour behind it. The paper discusses differences in breeding timing, seasonal habitat use and mate choice as possible reasons that neighbouring giraffes rarely mix. Repeated observations of identified animals near contact zones, combined with parentage information, could test which giraffes meet and which leave offspring together. Meeting and successful reproduction would need to be measured separately.
The timing of individual ancestry offers another question. DNA inherited from a recent ancestor tends to occur in longer stretches, which reproduction breaks into smaller pieces over generations. More detailed genomes and better sampling of possible source populations could help estimate when Nubian ancestry entered particular reticulated families. Such dates would depend on how well researchers could distinguish the source ancestries and model the reshuffling of DNA.
Finally, a broader sample across Laikipia could show whether the strongest Nubian signals are concentrated in a few families or occur more widely. That comparison would help separate the exceptional individuals from the older history shared by the region's giraffes. Coimbra and colleagues have provided the evidence needed to ask both questions without treating every trace of shared ancestry as the same biological event.
Sources
- Raphael T. F. Coimbra, Sven Winter, Arthur Muneza, Stephanie Fennessy, Moses Otiende, Domnic Mijele, Symon Masiaine, Jenna Stacy-Dawes, Julian Fennessy and Axel Janke (2023). Genomic analysis reveals limited hybridization among three giraffe species in Kenya. BMC Biology 21:215. DOI: 10.1186/s12915-023-01722-y.
- Alice Petzold and Alexandre Hassanin (2020). A comparative approach for species delimitation based on multiple methods of multi-locus DNA sequence analysis: A case study of the genus Giraffa (Mammalia, Cetartiodactyla). PLOS ONE 15(2):e0217956. DOI: 10.1371/journal.pone.0217956.
- Sam van Giessen, David Prochotta, Menno Jeroen de Jong, Richard Harvey, Megan Claase, Julian Fennessy and Axel Janke (2026). Genomic insights into the persistence of Nubian giraffe (Giraffa camelopardalis camelopardalis) in conflict-affected South Sudan. Scientific Reports 16:27825. DOI: 10.1038/s41598-026-66559-1.
