Specieswatch: spring ice has made life hard for the common frog

Many common frogs were trapped under ice in early March and some inevitably died

Paul Brown

Tue 27 Mar 2018 21.30 BSTLast modified on Tue 27 Mar 2018 22.00 BST

The common frog Rana temporaria is having a difficult spring. The extreme cold at the beginning of March trapped many under ice. A lot continued to breathe through their skin, but after several days some died from lack of oxygen. The survivors then got breeding under way in many ponds, only for another three-day cold snap to halt proceedings. Some ponds still have no spawn, while in others the adults have already left piles of jelly to take their chance.

After years of observation – at least in parts of central England – it appears frogs that breed in shallow ponds that often dry out in the summer are the first to lay their eggs. The tadpoles have the advantage that there are few predators in a seasonal pond, but to survive they may have to develop extremely quickly if the spring and early summer are unduly dry. It seems hardly credible that the adults sense this and breed early, but in many deeper ponds that are never allowed to dry out, particularly in gardens, the frogs habitually mate later. Both breeding strategies seem to work, but which is most successful is hard to tell. Perhaps it varies each year depending on the weather.

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Bats anticipate optimal weather conditions

September 20, 2017

Millions of animals fly, swim or walk around the Earth every year. To ensure that they reach their destination, they need to perceive precise changes in environmental conditions and choose the right moment to set off on their journey. Bats, too, are influenced by environmental factors. Every spring, common noctules in southern Germany set off for their summer territories. Researchers at the Max Planck Institute for Ornithology in Radolfzell have been studying what conditions trigger this migration. They discovered that the decision to set off depends on a combination of wind speed, wind direction and air pressure. The researchers have developed a model that allows them to predict when the bats will start their migration.

Flocks of birds in the skies are a familiar autumn sight, as they head south to overwinter. But every year millions of other animals – from crabs and insects to fish and mammals – set off on a similar migration. There are a range of different factors which determine when they set off. Migratory birds, for example, need to have gained sufficient weight since the previous winter. When they depart is also affected by day length, wind conditions and air pressure. Bat migration, by contrast, is less well understood.

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Water voles 'decline by a fifth'

Water voles have declined by a fifth in the UK since 2011, a survey suggests.

Conservationists say that habitat loss, predation by American mink, and changeable weather are to blame.

The research was carried out by the Environment Agency and Wildlife Trusts, who are working to create more vole-friendly waterways.

Earlier reports had suggested that the animals were making a comeback. Conservationists say more needs to be done to save this species.

Alastair Driver, National Conservation Manager from the Environment Agency, said: "This creature is part of our waterway systems. People love walking along a canal and hearing the plop of a water vole into the canal. They are part of the food chain... part of the ecosystem.

"It would be a real shame to let that go."

'Ratty'

Water voles, immortalised by Ratty from Wind in the Willows, were once a common sight in the UK's waterways.

But since the 1970s, water vole numbers are thought to have declined by more than 90%.

Continued

An early spring drives butterfly population declines

Early snow melt triggers chains of events resulting in population declines in the mormon fritillary butterfly -- Study published early online in Ecology Letters

Stanford Univ (USA), March 15, 2012 –Early snow melt in the Colorado Rocky Mountains initiates two chains of events resulting in population decline in the mormon fritillary butterfly,Speyeria mormonia. One effect of snow melt date was readily detectable, but the second, cryptic effect required an understanding of the butterfly's biology. "This suggests that predicting effects of climate change on organisms' population sizes will be difficult in some cases due to lack of knowledge of the species' biology," noted Dr. Carol Boggs, professor in the department of biology at Stanford University and lead author on the study.

The study results are published early online in the journal Ecology Letters.

An initial understanding of the butterfly's life cycle and the factors determining egg production aided the research. Butterflies lay eggs (and then die) in the first summer; the caterpillars over-winter without eating and develop into adults in the second summer. In the laboratory, the amount of nectar a female ate determined the number of eggs she laid. This suggested that flower availability might be important to changes in population size.

Using long-term data on date of snow melt, butterfly population sizes, and flower numbers at the Rocky Mountain Biological Laboratory (RMBL) - located at 9,500 feet in the Colorado Rocky Mountains - researchers uncovered multiple effects of a single weather event, the date of snow melt, on change in population size of Speyeria mormonia butterflies. Early snow melt in the first year leads to lower availability of the butterfly's preferred flower species, due to exposure of newly developing plants to early-season frosts that kill flower buds. The researchers showed that reduced flower (nectar) availability per butterfly adversely affected butterfly population growth rate. Early snow melt in the second year of the butterfly life cycle worsened this impact, probably through direct killing of caterpillars during early-season frosts. The combined effects of snow melt in the two consecutive years explained more than four-fifths of the observed variation in population growth rate. "It is very unusual for research to uncover such a simple mechanism that can explain almost all of the variation in growth rate of an insect population", said Dr. David Inouye, professor of biology at the University of Maryland and co-author of the study.

"One climate parameter can have multiple effects on an organism's population growth," Dr. Boggs stated. "This was not previously recognized for species such as butterflies that live for only one year. We already can predict that this coming summer will be a difficult one for the butterflies, because the very low snowpack in the mountains this winter makes it likely that there will be significant frost damage."

"Long-term studies such as ours are important to understanding the 'ecology of place' and the effects of weather and possible climate change on population numbers," commented Dr. Inouye. "Research of this nature is critical to assessing the broader effects of weather on an ever-changing earth, and field stations such as RMBL, by facilitating longer-term, longitudinal studies, are an invaluable asset in this regard."

http://www.eurekalert.org/pub_releases/2012-03/bm-aes031412.php