Tag Archives: Cornwall

How long-tailed tits avoid inbreeding

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This 23 October 2015 video from Cornwall, Britain is called Long-tailed tits in the garden.

From the University of Sheffield in England:

Long-tailed tits avoid harmful inbreeding by recognising the calls of relatives

June 25, 2020

Long-tailed tits actively avoid harmful inbreeding by discriminating between the calls of close family members and non-family members, according to new research from the University of Sheffield.

Inbred animals typically suffer from reduced survival and reproductive success, so inbreeding is usually avoided. But, in species where young stay close to where they were born, relatives are often encountered as potential mates, increasing the risk of harmful inbreeding.

Long-tailed tits often breed close to home, allowing kin to help raise each other’s chicks, but also incurring a risk of inbreeding that reduces the reproductive success of offspring. The research, led by Dr Amy Leedale from the University of Sheffield’s Department of Animal and Plant Science, found that despite this risk, close relatives are actively avoided when pairs form each spring.

Long-tailed tits use distinctive calls to recognise close relatives so that they can help raise their offspring. The authors suggest that these calls also explain how the birds avoid inbreeding.

Dr Amy Leedale, who led the research as a PhD student at the University of Sheffield, said: “We recorded the calls of males and females in many pairs of long-tailed tits and found that the calls of breeding pairs were less similar than the calls of close relatives that they could have bred with. Call similarity within breeding pairs was, instead, similar to that observed among distant relatives or unrelated birds.”

Long-tailed tit calls are learned in the nest, when parents, offspring and siblings are closely associated. Call similarity can therefore act as a reliable indicator of close relatedness in adulthood. This study reveals a potential mechanism by which long-tailed tits can avoid harmful inbreeding as well as gaining benefits from cooperating with kin.

Professor Ben Hatchwell, who has led the long-tailed tit project at the University of Sheffield for more than 25 years, said: “This study demonstrates the value of long-term studies of wild animals, allowing us to build pedigrees of known individuals over many generations, and to measure the consequences of behavioural decisions for their reproductive success.”

Saving porpoises from fishing nets

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This 2016 video says about itself:

Why is by-catch a problem for porpoises?

Porpoise biologist Dr. Anna Hall explains why by-catch (entanglement in fishing nets) is such a big issue for porpoises. To learn more about porpoises, visit here.

From the University of Exeter in England:

‘Pingers’ could save porpoises from fishing nets

May 13, 2020

Underwater sound devices called “pingers” could be an effective, long-term way to prevent porpoises getting caught in fishing nets with no negative behavioural effects, newly published research suggests.

The study of harbour porpoises off Cornwall found they were 37% less likely to be found close to an active pinger.

Concerns have been raised about porpoises becoming used to pingers and learning to ignore them, but the eight-month study — by the University of Exeter and Cornwall Wildlife Trust — found no decrease in effectiveness.

There have also been worries that continual pinger use could affect porpoise behaviour by displacing them from feeding grounds, but when pingers were switched off the animals returned “with no delay”.

The effect was found to be “very localised” — the 37% reduction in porpoise detection at the active pinger compared to a drop of 9% just 100 metres away.

Harbour porpoises are the most common cetaceans (whales, dolphins and porpoises) seen at the Cornish coast, where accidental catching by fishing boats (“bycatch“) is a persistent problem.

“Cornwall Wildlife Trust have been monitoring local dolphin and porpoise deaths through our standings scheme for over 25 years, and bycatch is still the biggest threat to these animals in the South West with large numbers washing ashore every year,” said Ruth Williams, of Cornwall Wildlife Trust.

“Together with other NGOs we have campaigned to try to find a solution to reduce bycatch, that will work in our inshore fisheries.

“The results of this latest research show that there is a practical solution that is both effective and does not impact or change the animals’ behaviour, a positive result for both conservation and fishermen alike.” Lead author Dr Lucy Omeyer, of the University of Exeter and Fishtek, said: “Based on our findings, it seems likely that pingers would reduce harbour porpoise bycatch in gill-net fisheries with no negative consequences.

“Indeed, we found no evidence that long-term and continual use decreased the effectiveness of pingers or affected harbour porpoise behaviour.”

Pingers are acoustic deterrent devices which are fitted on to fishing nets.

They work by emitting a randomised sonic noise, or “ping”, which can be heard by dolphins and porpoises and highlights the presence of the nets, thereby preventing accidental entanglement.

The porpoises’ own click sounds can be way above 100 times louder than the pings from the pinger.

In the study, Fishtek Banana Pingers were placed in the water along with two acoustic loggers (one beside the pinger and one 100m away) to record cetacean activity.

With small-scale operations the main form of fishing in UK waters, the researchers say there is an “acute need” for cost-effective strategies to prevent bycatch, such as pingers.

The study was partly funded by Whale and Dolphin Conservation.

Cornwall Wildlife Trust’s marine strandings report recorded 245 cetacean strandings in Cornwall in 2019.