There are three species of right whale – two are at risk (Picture: Getty/iStockphoto)
A critically endangered species of whale is getting smaller – and producing fewer babies as a result.
There are thought to be only around 360 North Atlantic right whales left in the world – named because they were the ‘right’ whale to hunt due to their size and slow speed.
To stop the decline, around 50 calves must be born each year. However, the National Oceanic and Atmospheric Administration (NOAA) reports just 17 have been born this season.
In 2021, research highlighted that the whales have been getting smaller since 1981, with some showing signs of severely stunted development.
Now, a new study by scientists across the globe has found the whales’ decreasing size is impacting their ability to reproduce.
Analysing data collected from 1970 to 2020, including aerial photos used to measure their length, the team used statistical modelling to understand various indicators of health and reproductive success.
North Atlantic right whales are critically endangered (Picture: Getty/iStockphoto)
The results showed that while a 14-metre female had a 56% chance of giving birth, that figure fell to 11% for an 11-metre whale.
Lead author Dr Enrico Pirotta, from St Andrews University, said: ‘In this paper we provide strong evidence that the declining trend in right whale calving probability is associated with the decreasing body size of individuals in this population.
North Atlantic right whales: the lowdown
The North Atlantic right whale, or Eubalaena glacialis, is one of three species of right whale alongside the Southern and North Pacific right whales – the latter is also endangered.
They can grow up to 16m long, and weigh more than 60 tonnes. They have large, stocky bodies with no dorsal fin.
They eat zooplankton, krill and other small invertebrates.
Right whales can live up to 70 years old, but may live longer.
‘This adds to previous evidence indicating that their health is also declining.’
North Atlantic right whales were previously hunted almost to extinction, but have been protected since 1972 – but unlike many other species of whale, their numbers have failed to recover.
Right whales are particularly vulnerable to ship strikes and entanglements in fishing gear due to their habitat, which includes the east coast of North America and west coast of Europe.
Right whales were named because they were the ‘right’ size to hunt (Picture: Getty/iStockphoto)
However, factors such as climate change and other human stressors such as noise pollution are thought to be impacting their health – leading to smaller body size.
‘These whales rely on stored energy resources to support the costs of reproduction,’ said Dr Pirotta, speaking to Metro.co.uk. ‘Being smaller means that a female can accumulate less energy in absolute terms, which in turn could affect her ability to successfully breed.’
The collaborative study, funded by the US Office of Naval Research, aims to understand the effects of stressors on marine mammals.
Whales are vulnerable to ship strikes (Picture: Getty)
Dr Pirotta added: ‘In terms of implications for the conservation of the species, there is ample evidence that human activities in the ocean affect the survival of North Atlantic right whales, in particular through entanglement in fishing gear and collisions with vessels.
‘Mitigation measures should be put urgently in place to reduce these sources of mortality.
‘However, our results suggest that management policies are also needed to enhance individual health and growth, so that females can achieve higher rates of reproduction that will ultimately be necessary to support the species’ recovery.’
The study is published in the journal Royal Society Open Science.