--- title: "Southern Right Whale Calf Deaths Exceed Previous Records" url: https://newscentral.site/southern-right-whale-calf-deaths-exceed-previous-records/ language: en publisher: "News Central Site" section: "Science" published: 2026-10-14T09:00:00.000Z updated: 2026-10-14T09:36:01.216Z id: e9efd26a-8fac-4dc5-8e70-544963568f4f source: "Live Science https://www.livescience.com/animals/whales/hundreds-of-whale-calves-have-mysteriously-died-in-patagonia-and-scientists-are-racing-to-find-out-why" attribution: "Link to https://newscentral.site/southern-right-whale-calf-deaths-exceed-previous-records/ and name News Central Site when you quote or summarize this story." --- # Southern Right Whale Calf Deaths Exceed Previous Records More than 300 southern right whale calves have died in Argentine Patagonia since June, exceeding previous records of annual die-offs for this species. The unprecedented number of deaths has left scientists racing to determine the cause behind the tragic event, which has far surpassed the previous record set in 2012 when 113 southern right whale calves perished. Laboratory tests on specimens from this year's deceased whales have revealed that they tested positive for Erysipelothrix rhusiopathiae, a pathogenic bacterium previously identified in these animals in 2013. Researchers are still trying to understand what might have triggered the sudden and massive die-off of southern right whale calves, despite knowing that the bacterium has been present in this species since 2013. The urgency of finding an answer is driven by the need to comprehend not only the threat facing this particular species but also its potential impact on the wider ecosystem and human populations. The first signs of trouble appeared on the beaches of Península Valdés in June, as the breeding season got underway and southern right whales began to arrive. This region in Chubut province, northern Patagonia's coastline, is a crucial habitat for these marine mammals. Normally, calf mortality rates range from 20% to 30% of a cohort due to various causes, such as infections. However, this year's losses have already exceeded those numbers significantly. In September, a survey by CESIMAR's Marine Mammal Laboratory counted 409 calves among a total of 1,375 southern right whales. With over 300 deaths recorded so far, the die-off represents an unusually high proportion of these young animals. The final tally will be released in December by the Southern Right Whale Health Monitoring Program. Scientists are working to accelerate their research and determine what's behind this year's exceptional mortality rate compared to previous years. Analyses of samples sent earlier than usual have revealed that the calves died from erysipelas, a bacterial infection affecting the skin. The bacterium E. rhusiopathiae, responsible for causing erysipelas in whale calves, is not exclusive to marine mammals and can be found in various aquatic environments. This opportunistic pathogen thrives in a wide range of animals, including fish, crustaceans, birds, and even pigs, which serve as its natural reservoirs. The growth of gull populations in Patagonia has been linked to increased food availability, thanks to fishing activities and discarded catch. This has led to the emergence of new breeding colonies in the region. However, while the presence of gulls is a regular part of the ecosystem, their attacks on whale calves alone do not explain the recent die-off event. To investigate the role of gulls in the mortality event, scientists plan to take swabs from the birds to check for E. rhusiopathiae, a bacterium that has been implicated in the deaths. The results could help inform a management strategy for the gull population and potentially shed light on the die-off. Marine biologist Diego Rodríguez believes that research should focus not just on the dead calves, but also on the broader ecosystem to understand where E. rhusiopathiae is present and how it might be spreading. Rodríguez suggests that cross-infection could be a key factor in the die-off event. Scientists are still trying to determine what specific factors might have contributed to this year's widespread infection by E. rhusiathiae, which has been present in the ecosystem for some time. It is thought that multiple factors may be at play, rather than a single cause. Researchers agree that having identified the bacterium as the likely culprit is an important step forward, but they still need to understand what changed this year to trigger such a severe die-off event. Changes in environmental conditions may be contributing to the mass die-off of whale calves in Patagonia. Researchers suggest that shifts in water temperature, salinity, pH levels, or rainfall could alter the likelihood of infection by the bacterium Erysipelothrix rhusiopathiae. Another possibility is that the pathogen itself has changed, either through the emergence of a more virulent strain or a different serotype. This could be influenced by various factors, including changes in food availability and the mothers' body condition, which may make their calves more vulnerable to infection. The El Niño phenomenon may also play a role in altering oceanographic conditions and food availability, although researchers acknowledge that there is currently insufficient evidence to link it directly to the die-off. Further investigation is needed to determine whether this factor is contributing to the crisis. Experts are cautious about predicting the long-term impact of this die-off on the southern right whale population. Losing such a large proportion of a season's calves could have significant demographic consequences, potentially leading to a reduced number of adults in future populations. However, some researchers argue that a single season of exceptionally high mortality does not necessarily mean the overall population will decline. Southern right whales are known for their long lifespan, and calves represent only a small fraction of the total population. The die-off also raises concerns about public health, as the bacterium Erysipelothrix rhusiopathiae can infect humans through skin wounds or contact with infected animals or contaminated seawater. The mysterious deaths of hundreds of whale calves in Patagonia have sparked an urgent investigation by scientists. Preliminary findings suggest that a bacterial infection may be responsible for the die-off, although further research is needed to confirm this theory. The bacterium Erysipelothrix rhusiopathiae, which can infect humans through skin wounds or contact with infected animals or contaminated seawater, has raised public health concerns in addition to its potential link to the whale calf deaths. --- Source: [Live Science](https://www.livescience.com/animals/whales/hundreds-of-whale-calves-have-mysteriously-died-in-patagonia-and-scientists-are-racing-to-find-out-why) Published by News Central Site: https://newscentral.site/southern-right-whale-calf-deaths-exceed-previous-records/