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Genetic study explains the origin, adaptation, and fate of the herd that lived isolated on Amsterdam Island since 1871, as well as detailing the decisions made to preserve the local ecosystem.
A genetic analysis revealed new details about a herd of cattle that remained isolated for more than 130 years on Amsterdam Island, a subantarctic territory located in the southern Indian Ocean. At first glance, it seemed unlikely that just five animals could survive for so many decades in such an extreme environment. However, when the DNA of this herd was analyzed, researchers found explanations for their resilience, adaptation, and population growth until the final removal of the last specimens in 2010, during an environmental conservation project.
According to the researchers, the results were obtained through genome sequencing of samples preserved over the last decades. Additionally, the conclusions reinforce the role of genetics in understanding the adaptation of isolated populations. The information was released by the scientists responsible for the study and is aligned with historical records on the occupation and management of Amsterdam Island.
How the herd arrived on Amsterdam Island
In 1871, a farmer transported five cattle to Amsterdam Island with the aim of starting a colonization project. However, a few months later, the initiative failed and was abandoned. Thus, the animals remained completely alone, without any human management.
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Despite adverse conditions, the herd survived and expanded over the decades. Later, the population reached about 2,000 individuals at two distinct times: 1952 and 1988.
Among the main historical milestones are:
- 1871: five cattle were left on the island after the colonization failed.
- 1952 and 1988: the population reached approximately 2,000 animals.
- 2010: the last specimens were removed to allow the environmental recovery of the island.
What the genetic analysis discovered
Additionally, the study revealed that the herd had a much more diverse genetic origin than previously imagined.
About 75% of the DNA showed characteristics of European taurine cattle, similar to the current Jersey breed. On the other hand, approximately 25% of the genetic material showed a strong relationship with zebus originating from the Indian Ocean region, including animals associated with Madagascar.
Thus, the researchers concluded that the five founding animals already had a mixed genetic heritage even before arriving on the island.
How the animals overcame low genetic diversity
Initially, the isolation of only five animals caused an estimated inbreeding rate of about 30%.
However, as indicated by the study, the rapid population expansion reduced the risk of permanently losing genetic diversity.
Furthermore, the complete genome sequencing pointed out important characteristics:
- Preserved physical vigor, even during the initial period of high inbreeding.
- Reproduction concentrated in four months of the year.
- Genetic changes related to the nervous system, associated with behavioral adaptation.
According to the researchers, these characteristics favored the group’s survival in a humid, windy environment without human intervention.
Was there island dwarfism?
For years, there was a hypothesis that the herd had rapidly decreased in size due to isolation.
However, this hypothesis was not confirmed by genetic analysis.
According to the results, the cattle introduced in 1871 already belonged to naturally smaller lineages. Additionally, signs of natural selection were identified mainly in genes linked to the central nervous system, indicating important behavioral adaptations for survival.
Among the main conclusions are:
- No genetic evidence of accelerated island dwarfism was found.
- Adaptations related to the central nervous system were identified.
- Behavioral changes favored survival without human management.
Why was the herd removed?
From the late 1980s, environmental managers observed that the herd was causing increasing impacts on the native vegetation and the island’s birds.
Initially, the area was divided by fences to reduce damage. Subsequently, the complete removal was carried out in 2010, prioritizing the recovery of the ecosystem.
Currently, environmental restoration work continues to be developed on Amsterdam Island with a focus on preserving local fauna and flora.
The information presented is based on the results of the genetic study conducted by researchers responsible for analyzing the cattle genome, as well as historical records on the occupation of Amsterdam Island and the environmental conservation actions conducted in the territory.
