Panamanian city frogs more attractive


This February 2018 video from the USA says about itself:

The Túngara Frog‘s “Taste For the Beautiful”

Department of Integrative Biology faculty member Michael J. Ryan discusses animal sexual selection and evolution in his new book “A Taste for the Beautiful”. Ryan is the Clark Hubbs Regents Professor in Zoology at The University of Texas at Austin and a Senior Research Associate at the Smithsonian Tropical Research Institute in Panama. He is a leading researcher in the fields of sexual selection, mate choice, and animal communication.

From the University of Texas at Austin in the USA:

Females prefer city frogs’ tunes

December 10, 2018

Urban sophistication has real sex appeal — at least if you’re a Central American amphibian. Male frogs in cities are more attractive to females than their forest-frog counterparts, according to a new study published in Nature Ecology and Evolution.

Frogs in urban areas have more conspicuous and complex vocal calls, in part because they have fewer predators than those in natural habitats, say scientists from Vrije Universiteit (VU) in the Netherlands, The University of Texas at Austin, Purdue University and the Smithsonian Tropical Research Institute in Panama.

University of Texas at Austin professor of integrative biology Mike Ryan joined team leader Wouter Halfwerk and colleagues to investigate how city life has altered the signaling behavior of male túngara frogs. The trappings of cities often interfere with animal communication, as noise and light pollution affect the visual and auditory signals animals use to attract mates. Halfwerk previously has published work showing how urbanization affects birdsong in Europe.

The research team recorded the characteristic ‘chuck’ calls made by the one-inch frogs living in forests near the Panama Canal and in nearby human-disturbed areas, including small towns and cities. They found that the urban males would call more often and with greater call complexity, meaning they made more of the ‘chuck’ sounds that females prefer, compared to the frogs in the forest. The authors played back both calls to female frogs in a lab, and they discovered that three-quarters of the females were more attracted to the complex urban calls, compared to the simpler forest calls.

“In the forest, these more attractive calls have a higher cost,” Ryan explained. “The sound can attract frog-eating bats and bloodsucking midges.”

Evolution may select for the trait that allows the frogs to make more complex vocal calls in cities and towns, where the eavesdropping predators are scarcer there than in the forest. To help test this idea, the researchers examined what would happen when they moved urban frogs into forest habitats and forest frogs into urban habitats. It turned out that the urban frogs were able to actively reduce the complexity of their calls in the new environment, but forest frogs couldn’t make the switch to making their calls more complex to attract females.

Ryan, his graduate students and colleagues have been studying sexual selection and communication in the túngara frog for decades. His 2018 popular science book A Taste for the Beautiful describes how males of this species and other species have evolved over the years to attract more females.

Advertisements

Brazilian tree frogs parenting, new study


This June 2015 video says about itself:

7 Tiny Frogs Found on 7 Brazilian Mountains

Researchers in Brazil discovered seven never-before-seen species of Brachycephalus frog on seven different mountains in the Atlantic forest.

From PLOS:

Not too big, not too small: Tree frogs choose pools that are just right

Frogs breeding in pools of water on leaves face trade-off between drying out and repelling predators

December 5, 2018

Frogs that raise their young in tiny pools of water that collect on plant leaves must make a delicate trade-off between the risk of drying out and the risk of being eaten, according to a study publishing December 5 in the open-access journal PLOS ONE by Mirco Solé from the Universidade Estadual de Santa Cruz in Bahia, Brazil and colleagues.

The temporary pools of water trapped by the leaf rosette of some plants in the Bromeliaceae family are used by a variety of creatures as a source of prey, water and shelter — one example is the Broad-snout casque-headed Tree Frog (Aparasphenodon arapapa) which uses the water ‘tanks’ of bromeliad plants as a place to mate and rear its tadpoles. To understand how the frogs choose the right spot, the researchers measured the characteristics, including size, water level, and leaf debris, of the central tanks of 239 bromeliads in Reserve Boa União in Bahia, Brazil.

They compared bromeliads that were occupied by a tree frog with those that were empty and found that male frogs generally prefer bromeliads with larger tanks, a higher volume of water, and less leaf litter — qualities which make the tanks less likely to dry up and easier to access. However, the very largest and fullest bromeliad tanks were frog-less, suggesting that a trade-off exists when choosing the best place to breed. Males have a specially shaped bony head that they use to form a tight seal with the opening of the bromeliad tank, which is thought to protect them from predators. Forming a tight seal may be tricky in very large bromeliads, making them a poor choice as a shelter.

The authors conclude that the trade-offs animals face when selecting a site to breed should be taken into consideration in conservation strategies.

Solé adds: “Aparasphenodon arapapa, a tropical frog from the Brazilian Atlantic Forest places its eggs into bromeliads, but instead of simply choosing the largest bromeliad tank with the most water, complex trade-offs between selection pressures and balancing water requirements are involved in the bromeliad choice.”

Dinosaur age and modern frog discoveries


This 14 June 2018 video says about itself:

Frogs trapped in amber for 99 million years are giving a glimpse of a lost world. The tiny creatures have been preserved in sticky tree resin from the later part of the Age of the Dinosaurs.

From the Florida Museum of Natural History in the USA:

Amber fossils provide oldest evidence of frogs in wet, tropical forests

June 14, 2018

Summary: 99-million-year-old amber fossils from Myanmar provide the earliest evidence of frogs in wet, tropical forests.

About 99 million years ago, a tiny juvenile frog in present-day Myanmar was suddenly trapped in sap with a beetle, perhaps its intended next meal.

Unlucky for the frog, but lucky for science.

An extinct species now named Electrorana limoae, it’s one of four fossils that provide the earliest direct evidence of frogs living in wet, tropical forests and are the oldest-known examples of frogs preserved in amber.

“It’s almost unheard of to get a fossil frog from this time period that is small, has preservation of small bones and is mostly three-dimensional. This is pretty special,” said David Blackburn, study co-author and the associate curator of herpetology at the Florida Museum of Natural History. “But what’s most exciting about this animal is its context. These frogs were part of a tropical ecosystem that, in some ways, might not have been that different to what we find today — minus the dinosaurs.”

The findings and species description were published today in Nature’s Scientific Reports.

Frogs have been around for at least 200 million years, but glimpsing their early heyday is tough. Often small and lightly built, frogs don’t tend to preserve well. The frog fossil record skews toward more robust species from arid, seasonal environments, although the bulk of frog diversity today lives in tropical forests.

“Ask any kid what lives in a rainforest, and frogs are on the list”, Blackburn said. “But surprisingly, we have almost nothing from the fossil record to say that’s a longstanding association.”

The amber deposits of northern Myanmar in Southeast Asia provide a unique record of ancient forest ecosystems, with fossil evidence of mosses, bamboo-like plants, aquatic spiders and velvet worms. The discovery of Electrorana and the other fossils, the first frogs to be recovered from these deposits, help add to our understanding of frogs in the Cretaceous period, showing they have inhabited wet, tropical forests for at least 99 million years.

Frogs in amber are quite rare, with previous examples found in the Dominican Republic and Mexico and dating back only about 40 million and 25 million years, respectively.

Less than an inch long, Electrorana is the most well-preserved of the group. Clearly visible in the amber are the frog’s skull, its forelimbs, part of its backbone, a partial hind limb and the unidentified beetle. The other amber fossils contain two hands and an imprint of a frog that likely decayed inside the resin.

But Electrorana raises more questions than it answers, Blackburn said.

Many characteristics herpetologists use to discern details of a frog’s life history and determine how it’s related to other frogs — wrist bones, the pelvis, hip bones, the inner ear, the top of the backbone — are either missing or were not yet fully developed in the juvenile frog.

The existing bones provide clues about Electrorana’s possible living relatives, Blackburn said, but the results are puzzling: Species that have similar features include fire-bellied toads and midwife toads — Eurasian species that live in temperate, not tropical, ecosystems.

Gathering CT skeletal data for both living and extinct frogs, one of Blackburn’s long-term projects, could help illuminate ancient evolutionary relationships, possibly clarifying how Electrorana fits into the frog tree of life.

In the meantime, Blackburn nurtures the hope that other frogs in amber will be discovered, making Electrorana more than a one-hit wonder.

“We don’t have a lot of single-species frog communities in forests. It seems extremely unlikely that there’s only one. There could be a lot more fossils coming.”

In a new study, researchers have investigated how the endocrine-disrupting substance linuron affects reproduction in the West African clawed frog, Xenopus tropicalis. The scientists found that linuron, which is used as a pesticicide, impaired the males’ fertility, and that tadpoles developed ovaries instead of testicles to a greater extent, which caused a female-biased sex ratio: here.

Poison dart frogs’ colours, also camouflage


This 2016 terrarium video says about itself:

Dendrobates tinctorius ‘Powder Blue’ Calling.

Male dart frog vocalizing while female (barely seen) climbs the glass attempting to get to him.

From the University of Bristol in England:

Bright warning colors on poison dart frogs also act as camouflage

June 4, 2018

Poison dart frogs are well known for their deadly toxins and bright colours, which have made them a classic example of warning coloration.

The Dyeing Dart Frog, for example, is highly toxic and warns its predators with a bright yellow-and-black pattern.

However, new research led by scientists at the University of Bristol has revealed that the colour pattern does more than simply signal “danger.” Counterintuitively, it also works as camouflage.

Lead author, Jim Barnett completed this research, published today in the journal Proceedings of the National Academy of Sciences, while studying for a PhD at Bristol. He is now based at McGill University in Canada.

He said: “Effective as warning signals are, it’s not necessarily the best strategy to be maximally conspicuous.

Certain predators have evolved tolerance of toxins that would be deadly for humans, and some individual predators may have not encountered the warning signal prey before (a dangerous mistake for the predator, but also for the frog).

“So, colour patterns that could be distinctive close-up, but work as camouflage from a distance, would provide a clear advantage.”

Combining fieldwork in the jungles of French Guiana, computational modelling, and laboratory visual search experiments, Barnett and colleagues from the University of Bristol’s School of Biological Sciences and the School of Experimental Psychology investigated how the Dyeing Dart Frog uses its colours to balance the benefits of effective warning signals with the advantages of concealment.

They found that, despite being highly conspicuous at close range, the particular colours and their arrangement allow the pattern to blend together to form background-matching camouflage when viewed from a distance.

The frog’s pattern, therefore, allows it to get the best of both worlds: high fidelity camouflage until a predator discovers it, at which point its bright, highly salient, warning signal becomes clear.

Co-author Professor Innes Cuthill from the University of Bristol added: “How many other animals use ‘distance-dependent coloration’ to balance competing evolutionary pressures is yet to be explored.

“Being able to signal when close to a would-be mate, whilst remaining inconspicuous to more distant predators would seem beneficial. So too for human applications such as military camouflage, where recognition by allies is as important as concealment from foes. Also, signage that only need be clear at the distance where the information is needed, but might be distracting if detected earlier.”

Tree frog wakes up, video


This April 2018 video is about a tree frog waking up near the Loonse en Drunense Duinen nature reserve in North Brabant province in the Netherlands.

Toby Bissels made this video.

Moor frogs gathering


This April 2018 video shows blueish male moor frogs gathering in Twente region in the Netherlands for the mating season.

Harry Brummelhuis made this video.

Mating common frogs video


This is a video about mating common frogs in Wageningen, the Netherlands.

Frogs from groups exposed to a deadly virus are breeding at younger ages, new research suggests. Scientists studying European common frogs in the UK compared groups (“populations”) exposed to ranavirus and those free from the disease: here.