Tropical sea turtles discovered nesting in California for the first time in recorded history

Sea turtles usually found in the tropics have been spotted nesting on California beaches — a historical first, according to officials.

Olive ridley sea turtles are one of the smallest of the sea turtles and have distinctive olive-green, heart-shaped shells. They are typically found in tropical parts of the Pacific, Indian and Atlantic Oceans. But this month, two have come ashore in California.

An olive ridley turtle was seen digging a nest near Seal Beach National Wildlife Refuge in northwest Orange County last week, according to the US Fish and Wildlife Service.

A few days later, a nesting olive ridley was spied near the Huntington Beach Pier, also in Orange County. Originally, it was believed they were the same turtle, but an expert analysis of body shapes and unique shell patterns confirmed these were two different turtles.

Huntington Beach Fire Department

The sightings mark “the first-ever documented natural sea turtle nesting on the US West Coast,” the National Oceanic and Atmospheric Administration said in a social media post.

Olive ridley turtles are known for mass nesting, called “arribada,” where thousands come ashore at the same time to lay their eggs on a certain beach — a phenomenon that’s been observed in countries such as Costa Rica and Mexico. But it’s more common for the turtles to nest in a solitary way, which is what appears to have happened in California.

Scientists are still working to understand what pushed the turtles northward and whether this is an anomaly or potentially a more long-term expansion of their range as the human-driven climate crisis warms the oceans.

Their behavior was very likely influenced by the current super El Niño weather pattern , which has driven up ocean temperatures, said Jeffrey Seminoff, leader of the Marine Turtle Ecology & Assessment Program at NOAA.

But this is likely not the only reason. Sea turtles navigate the oceans “using multiple internal and environmental cues, including their own internal compass — sort of an on-board GPS — as well temperature, wave direction, time of year, etc.,” Seminoff said.

He believes a confluence of factors, including sustained warm water and “malfunctioning GPS,” likely led them to think they were coming ashore at nesting beaches in Mexico.

Allen J. Schaben/Los Angeles Times/Getty Images

Another theory is that Pacific storm activity could have pushed the turtles off course. The Pacific Ocean has been particularly busy recently as the exceptionally warm water brought by El Niño supercharges its hurricane season .

“Nothing is off the table in terms of causation. It will be so hard to unravel the specific reasons,” Seminoff said.

Each olive ridley nest usually contains around 100 eggs, and the sex of the baby turtles is affected by temperature . Warmer temperatures tend to produce more female turtles. For olive ridleys, temperatures around 87 degrees Fahrenheit and above will mean almost all hatchlings will be female.

An interagency team will monitor the California nests for the next 45-60 days, the typical incubation period. The nest sites have already been fenced off and people are being asked to give them space and avoid disturbing them, to give the baby turtles the best chance of hatching. In the US, sea turtles are protected under the Endangered Species Act.

“ As animals adapt in unexpected ways to changes in their natural world, humans will need to adapt and make space to ensure endangered and threatened species are given a fighting chance,” said Jeff Flocken, president and CEO of the Aquarium of the Pacific, a non-profit institution, in a statement .

“If they successfully hatch, these baby turtles will likely one day return to nest to carry on future generations on these very same beaches, giving us a remarkable opportunity to help a species expand its range and thrive.”

据官方消息，人们首次在加利福尼亚州的海滩上发现了通常生活在热带地区的海龟筑巢。

橄榄蠵龟是体型最小的海龟之一，它们有着独特的橄榄绿色心形背甲。它们通常生活在太平洋、印度洋和大西洋的热带海域。但本月，有两只橄榄蠵龟在加利福尼亚州登陆。

据美国鱼类和野生动物管理局称，上周有人在橙县西北部的海豹滩国家野生动物保护区附近看到一只橄榄蠵龟在挖巢。

几天后，在奥兰治县亨廷顿海滩码头附近又发现了一只正在筑巢的橄榄蠵龟。起初人们认为它们是同一只海龟，但专家对体型和独特龟壳纹路的分析证实，这是两只不同的海龟。

亨廷顿海滩消防局

美国国家海洋和大气管理局在社交媒体上发帖称，这些目击事件标志着“美国西海岸首次有记录的自然海龟筑巢”。

橄榄蠵龟以大规模筑巢而闻名，这种现象被称为“集体上岸产卵”（arribada），成千上万只海龟同时爬上岸，在特定的海滩上产卵——这种现象在哥斯达黎加和墨西哥等国都有观察到。但更常见的情况是，海龟单独筑巢，而加州的情况似乎正是如此。

科学家们仍在努力了解是什么原因促使海龟向北迁徙，以及这是否是一种异常现象，还是随着人类活动导致的气候危机使海洋变暖，海龟活动范围的长期扩张。

美国国家海洋和大气管理局 (NOAA) 海洋海龟生态与评估项目负责人杰弗里·塞米诺夫表示，它们的行为很可能受到当前超级厄尔尼诺天气模式的影响，这种天气模式导致海洋温度升高。

但这可能并非唯一原因。塞米诺夫说，海龟在海洋中导航“利用多种内部和环境线索，包括它们自身的内部罗盘——有点像车载GPS——以及温度、波浪方向、季节等等”。

他认为，持续温暖的海水和“失灵的 GPS”等多种因素的共同作用，可能导致他们以为自己是在墨西哥的筑巢海滩上岸。

艾伦·J·沙本/洛杉矶时报/盖蒂图片社

另一种理论认为，太平洋风暴活动可能使海龟偏离了航线。由于厄尔尼诺现象带来的异常温暖海水加剧了飓风季的活跃程度，太平洋近来尤为活跃。

“就因果关系而言，一切皆有可能。要查明具体原因将非常困难，”塞米诺夫说。

每个丽龟巢穴通常包含约100枚卵，幼龟的性别受温度影响。温度越高，雌龟的比例往往越高。对于丽龟来说，温度在华氏87度（约摄氏30度）及以上时，几乎所有孵化的幼龟都是雌性。

一个跨部门小组将对加州的海龟巢穴进行为期45至60天的监测，这通常是海龟的孵化期。巢穴周围已经设置了围栏，当局呼吁民众保持距离，避免打扰海龟，以确保幼龟有最佳的孵化机会。在美国，海龟受到《濒危物种法》的保护。

“随着动物以意想不到的方式适应自然环境的变化，人类也需要适应并腾出空间，以确保濒危物种和受威胁物种有机会生存下去，”太平洋水族馆（一家非营利机构）总裁兼首席执行官杰夫·弗洛肯在一份声明中表示。

“如果它们成功孵化，这些小海龟将来很可能会回到这些海滩筑巢，繁衍后代，这将给我们一个绝佳的机会，帮助一个物种扩大其分布范围并繁荣发展。”