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ABC News
20-05-2025
- Science
- ABC News
Humpback whales have babies much further south than previously thought
Humpback whales are on the move again. At this time of year, the whales travel up the eastern and western sides of Australia, treating viewers on the coast to a show. They're migrating from cold, krill-rich southern waters to spend their winters in the warmer seas north of the continent, which are the whales' breeding grounds. You may even see mums with newborn humpbacks on the northern route well before they reach the tropics, according to a new study. The study challenges assumptions about where humpback whales breed, and possibly why they migrate, according to lead author Jane McPhee-Frew. And observations by citizen scientists played a key role in the findings. Until now, many researchers believed whales only gave birth to calves in warmer tropical waters. But the study, published in Frontiers in Marine Science, found records of baby humpbacks in the east as far south as Tasmania and New Zealand. Humpback whales occur in every ocean around the world, with both northern hemisphere and southern hemisphere populations moving between their respective poles and the tropics. They were nearly hunted to extinction by the mid-20th century, but their numbers have since rebounded, with tens of thousands now migrating up the Australian coasts. Each year begin their northward migration from April, and return south between August and November. Around Australia, humpbacks generally weren't thought to give birth further south than 28 degrees latitude in the east (near the Gold Coast), or 23 degrees in the west (just south of Exmouth). "Our general concept of humpback whale ecology is that they feed at high latitudes in the poles, breed in the tropics, and they have this migration that's driven between the two needs," Ms McPhee-Frew said. Ms McPhee-Frew, a PhD candidate at the University of New South Wales, had been surprised to see a very young whale while working as a tour guide in Newcastle in 2023. "I saw a newborn right at the mouth of Newcastle Harbour," she said. Her PhD supervisor was also surprised, but Ms McPhee-Frew's colleagues in tourism weren't. They had apparently seen baby humpbacks in colder southern waters. This prompted Ms McPhee-Frew and fellow ecologists to search for more records of newborn whales south of the tropics. "We clearly have a gap here," she said. The researchers compiled records of baby humpback whales from a range of sources: government agencies, migration surveys and citizen science records from places like tourism boat trips. They found records of more than 200 newly-born whale calves appearing further south than the previously assumed limit. Some of the neonates were recorded at 43 degrees south, in the waters around Tasmania and New Zealand. This was as far south as the observations went, so it's possible that humpbacks were giving birth even closer to Antarctica. This means the whales don't need to breed in warmer waters — although they might prefer to. The baby whales were born while their mothers were heading north, towards the tropics. Olaf Meynecke, a whale researcher at Griffith University who wasn't involved in the study, said the results were "not surprising". Dr Meynecke and his colleagues had seen newly-born humpbacks well south of their traditional breeding grounds in the past decade, all heading north. "We know that they undertake all important behaviour — feeding, mating and birthing — not only in dedicated areas, but also along their migratory corridor," Dr Meynecke said. If the humpback whales don't need to breed in the tropics, why are they migrating thousands of kilometres to do it? "I don't know, but it's exciting," Ms McPhee-Frew said. It may be that whales born in the tropics are still better off. Ms McPhee-Frew pointed out a number of "really obvious" benefits to warmer waters: they're better for baby whales with poor temperature regulation, they're calmer, and they have fewer predators such as orcas. Dr Meynecke says that while humpbacks can give birth in cooler waters, they still migrate north to "ensure faster growth rates" for their calves. "With an expansion of the population and higher stress on food availability during summer feeding, it may be an advantage to give birth further south," Dr Meynecke said. But there could also be other factors driving the migration. "Is it that the female is just driven north through some deep either cultural or genetic instinct?" Ms McPhee-Frew said. Either way, studying baby whales born in cold waters will help researchers find out. If these calves grow up worse off than their warm-water peers, that will show that there really is a good reason to migrate for breeding, she said. "What we have now is this really important comparison group." Dr Meynecke wants to see systematic studies on the mothers and calves who are born mid-migration, to learn more about their true numbers and behaviours. He said it would be interesting to know the effect of being born during migration on an individual calf. "Will it return to the same waters where it was born for reproduction?" he asked. Ms McPhee-Frew, meanwhile, recommended that people keen to see whales book in tours with local responsible operating groups — both for the fun of seeing them, and because their observations may help further research. There are a number of citizen science projects in many states. If you're planning to do some whale watching this winter, you can help researchers wherever you are along the coast by logging your observations. If you're interested in drone photography, note there is a blanket rule of keeping drones at least 100m away from marine animals including whales. Each state may have additional rules. Ms McPhee Frew said photographers should include the distance (and zoom or photography settings) in the caption when posting pictures. "We encourage people to enjoy these lovely animals, provided they're following the rules that are in place for the whales' protection," she said.
Yahoo
07-04-2025
- Science
- Yahoo
White sharks make frequent visits to Maine's coastal waters, new data reveals
Apr. 7—Great white sharks appear to be using the shallow coastal waters next to some of Maine's most popular beaches in late summer while traveling between Cape Cod and Nova Scotia, most likely snacking on the growing seal populations in the Gulf of Maine. A team of New England scientists documented 107 white sharks off the coast of Maine, ranging from 7 to 16 feet in length, between 2012 and 2023, with most detected within a half mile from shore in less than 65 feet of water, according to a study published last month in Frontiers in Marine Science. But the total number of white sharks in Maine remains very low compared to known hotspots like Cape Cod or Hilton Head, according to the study's lead author, Matthew Davis of the Maine Department of Marine Resources. On average, Maine beaches had a tagged white nearby less than seven days a year. The relatively low numbers led the research team to conclude that Maine swimmers aren't at significant risk and, despite the documented presence of white sharks in the Gulf of Maine, there is no justification for regional anti-shark measures, like shark nets, even along Maine's most popular beaches. While most whites are not tagged and come and go without setting off the acoustic sensors, the data gives researchers a new picture of white shark prevalence and movements along the Maine coast. "We know a lot about white sharks in Cape Cod and Nova Scotia, but the Gulf of Maine has been sort of a black box of information up until now," Davis said. "This is the first time anyone has been able to track the movements of white sharks over time in the region." After a white shark killed a woman swimming off Bailey's Island in Harpswell in 2020 —Maine's only fatal shark attack on record — the Maine Department of Marine Resources launched a white shark study team and deployed acoustic sensors along the coast to track the activity of already-tagged white sharks. The department placed a sensor — think of them like a barcode reader with a big range — near sandy beaches, populated islands and seal haul-out sites, where the favored target of hungry adult white sharks are known to come ashore to rest, molt, breed and have pups. The sensors show white sharks like the same sandy beaches we do, including Ogunquit, Kennebunk, Higgins and Wells. In an average year, Ogunquit attracts seven tagged sharks over five days, compared to Kennebunk's six sharks in six days, Higgins' five sharks in five days and Wells' five sharks in four days. And many like to go when we do. Nearly half the sharks were detected near beaches visited during the daytime. Their numbers start to surge in June and drop off in October, preferring water that is between 55 and 60 degrees Fahrenheit, although some will stay through December. But it is important to note that the average shark detected near a Maine beach only hung out for about 15 minutes, Davis said. The average time spent out in the waters off Maine islands tended to be a little bit longer. In one rare case, a white shark hung out off the coast of Saco for more than a day. A private beach open to the public at the southwest tip of the Phippsburg peninsula — Head Beach — appears to be the most popular among white sharks, attracting 40 different whites over a three-year period, the study found. Sensors there detected an average of 17 sharks a year over 13 days. Surprisingly, nearby Popham only averaged three sharks a year, while Reid averaged only two. Ragged Island in eastern Casco Bay — notable as the one-time summer home of poet Edna St. Vincent Millay — reported the highest number of days of shark activity a year, with 12 sharks visiting over 30 days. Ragged is close to haul-out sites where seals come ashore to rest, breed and have pups. White sharks are not new to the Gulf of Maine, Davis said. Their numbers here are likely bouncing back because of conservation measures put in place for both white sharks, which were overfished until the 1990s, as well as seals, a favorite prey species for adult whites. Maine is located between three of the largest gray seal colonies in North America, with pupping surveys indicating a growing population in the region. Within the last decade, the harbor seal population has grown to more than 61,000. Like many of Maine's terrestrial visitors, white sharks tend to stick to southern and midcoast Maine locations. With one exception, no more than seven sharks were detected at any one Downeast location. Fewer acoustic receivers in these areas might help explain the relatively low detection rates. The sensors can detect a tagged shark up to 2,000 feet away. That means a tagged shark at some of Maine's longest beaches, like Ogunquit or Wells, could be missed. Most importantly, the study cannot paint a full picture of the white sharks in Maine because most of them aren't tagged at all. Davis said he would like to deploy more sensors in Downeast waters in the future. Copy the Story Link
Yahoo
20-03-2025
- Science
- Yahoo
A small amount of penguin poop is enough to spook krill
Although a single penguin is capable of devouring thousands of krill in a single sitting, swarms of the zooplankton may detect disturbances in the water ahead of mealtime. The telltale sign? Bird poop. That's what researchers at the Bigelow Laboratory for Ocean Sciences theorize after studying the movements of krill trawled from Antarctica's Bransfield Strait. According to their results, published March 20 in Frontiers in Marine Science, it only takes a small amount of penguin guano (poop) to influence the tiny sea creatures' behavior. 'Here we show for the first time that a small amount of penguin guano causes a sudden change in the feeding and swimming behaviors of Antarctic krill,' Nicole Hellessey, a corresponding author and postdoctoral researcher, explained in an accompanying statement. To test how krill respond to chemical evidence of nearby penguins, Hellessey and colleagues placed krill into an aquarium at Palmer Station on Antarctica's Anvers Island. They then separated out six-eight individuals and transferred them into a flume of seawater measuring 34.7 degrees Fahrenheit. To better replicate their usual environment, the team even dimmed the ambient lighting to mimic a depth of around 131 feet. Over multiple trials, researchers funnelled in seawater mixed with either algae, penguin poop, or a mixture of both while recording the results using a pair of automated cameras. Scientists then analyzed the footage based on selected krills' 3D positionality as well as the direction and speed of their swimming. The findings were clear. While krill generally swim straight upstream in what's known as rheotaxis, the presence of penguin guano appeared to immediately influence their behavior. More specifically, the krill sped up their swimming as much as 1.5 times faster than average while also making three times more turns at larger angles. The penguin poop didn't only influence krill movements. In another phase of the experiment, researchers noticed the zooplankton consumed 64 percent less algae after sensing what they thought may be nearby birds. This implies that krill engage in evasive maneuvers so much that they subsequently eat less when guano is in the water around them. 'Such behavior to escape from nearby penguins would greatly increase the krill's odds of survival,' said Hellessey. 'And these odds would increase exponentially in a swarm, if their neighbors could detect the same cues and communicate the danger to each other.' The defensive response is likely not only limited to penguins. Given the range of predators that regularly feed on krill, the team theorizes they likely exhibit similar behavior in the presence of seals, whales, and other Antarctic predators. As climate change continues to shift global ocean ecosystems, however, this detection ability may reduce a krill's chances for survival. Although the team hasn't identified the specific chemicals present in penguin poop that sends krill into a panic mode, they do know that rising acidification levels and warming temperatures could affect how the zooplankton sense danger. 'Any changes to krill's behavior could have major impacts on the future Southern Ocean, as Antarctic krill are a keystone species in this ecosystem,' Hellessey said. Regardless of further research results, one thing is apparently certain: Dealing with penguin poop is not an enjoyable experience.'Smells like rotten shellfish. Not pleasant to handle,' warned Hellessey.
