Fear of humans

28 08 2025

Many animals avoid contact with people. In protected areas of the African savanna, mammals flee more intensely upon hearing human conversations than when they hear lions or sounds associated with hunting. This fear of humans affects how species use and move in their habitat.

Throughout our lives, we interact with hundreds of wildlife species without stopping to think about it. These interactions can be direct, such as encountering wild animals while hiking in the mountains or driving through rural areas — or more deliberate, as when we engage with wildlife for food, sport, or trade. As hunters, fishers, and collectors, we kill more than 15,000 species of vertebrates — one-third of known diversity — a range of prey 300 times greater than that of any other predator our size (1).

Now, let’s look at it from the other side. Anyone who has survived an attack or a fatal accident, they understand that the experience is remembered for a lifetime. Likewise, animals store information about threatening or harmful encounters with humans (2). For them, adjusting their behaviour in response to human presence has implications for their survival and reproduction (3, 4), which are passed down from generation to generation (5). This ability to adapt, for example, determines which individuals, populations and species coexist with us in urbanised environments (6).

Response to dangerous sounds

Liana Zanette and her team measured the flight responses of wild mammals in the Greater Kruger National Park (South Africa) when exposed to sounds that signal danger (7) [video-summary]. To do this, Zanette recorded videos of more than 4,000 visits to 21 waterholes by 18 mammal species. During each visit, a speaker attached to a tree randomly played one of five playback sounds: hunting dogs barking, gunshots, lion growls, human conversations in a calm tone and, as a control, the songs of harmless birds.

Large mammals at waterholes in the Greater Kruger National Park (GPNK, South Africa) (7). GPNK covers an area of 1,800 km² to the east of Kruger National Park (19,500 km²). While Kruger is state-owned, GPNK is managed by private and community landowners. It has no fences, allowing free movement of animals between the two parks. The top three photos show: two lions (Panthera leo), a herd of African elephants (Loxodonta africana), and groups of common hippos (Hippopotamus amphibius) and African buffalo (Syncerus caffer). To study the flight response of Kruger’s mammals to threatening sounds (7), the bottom two photos illustrate the distance from the water to the speaker-video [ABR] device, which was secured to a tree inside a steel bite- and impact-proof case, and a leopard (Panthera pardus) fleeing after hearing a recorded human conversation, leaving behind an impala (Aepyceros melampus) it had just captured at a waterhole. The playback dialogues used in the experiment were in local languages: Afrikaans, English, Northern Sotho, and Tsonga. See documentaries on Kruger: (i) Aerial Africa: Kruger National Park, (ii) A guide to Kruger Park 2023 Wildlife and (iii) Exploring Klaserie: untamed & wild in the Greater Kruger. Overall, waterholes (see Kruger video-examples here, here and here), both natural and artificial, play a crucial role in shaping the ecology of African savannahs by influencing wildlife distribution, vegetation dynamics and overall ecosystem health. Photo credits: Naas Rautenbach (lions) and Liana Zanette.
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Categories : Africa, behaviour, biodiversity, conservation, environmental policy, exploitation, harvest, human-wildlife conflict, mammal, management, predation, predator, protected area, research, top-down ecology, trophic cascades

Trapped in the light

31 03 2025

Night is the peak activity period for many animal species. In the Western Andes of Ecuador, the Chocó golden scarab flies between forest patches during the night, but urban lighting interferes with their paths and jeopardises populations already struggling to persist in fragmented native forests.

Urban development has created a network of illuminated infrastructure that allows our society to function day and night without interruption. It is no surprise that with so much artificial light, we increasingly have to move farther away from towns and cities to see a sky full of stars.

Light pollution poses a challenge for nocturnal species that have adapted to living in the dimness of night (1, 2) — see documentaries about the impacts of artificial light on wildlife and insects, and a related scientific talk. This problem might be one of the causes of the global decline in insects (3, 4), in turn negatively affecting their role in maintaining agricultural systems through pest control, pollination, and soil quality (5). These concepts are featured by the documentaries The Insect Apocalypse and The Great Death of Insects.

Chocó golden scarab (Chrysina argenteola) walking on forest litter in La Maná (Cotopaxi, Ecuador). Growing to up to 4 cm in length, this species inhabits the tropical rainforest of the Chocó region in the Western Andes (10), where it is frequently attracted to artificial lights at night. The striking colour of this ‘jewel scarab’ is an optical illusion. The exoskeleton is covered with overlapping layers of chitin that polarise light and reflect hues of blue, gold, green, silver, or reddish tones, depending on the species (16). The metallic sheen appears to deter bird predation (17) and might serve as camouflage as well as aid in individual recognition (11). The eyes of insects are ‘compound’ — composed of 100s to 1000s of tubular eyelets (‘ommatidia’), each with its own cornea and lens (18), and all collectively contributing to insect vision. In nocturnal species like the golden scarab, the photoreceptor cells (at the base of each ommatidium) respond more slowly to light compared to diurnal species, allowing the former to collect more nocturnal light per unit of time before forming an image (19). However, just as staring at the sun blinds us, eyes adapted for night vision become overwhelmed by excessive artificial light, disrupting the behaviour of these species. Below the scarab image are two photographs contrasting the day and night landscapes of the same location in Pedro Vicente Maldonado (Pichincha, Ecuador) within the species’ distribution range. Photos courtesy of Martín Bustamante (animal) and Luis Camacho (city).

When flying, nocturnal insects orient their backs toward the sky, using the light of the moon and stars as a reference (6) (explained here and here). However, when they encounter artificial lights, they can no longer distinguish up from down, and so they can become disoriented, flying erratically, like a moth circling a streetlight.

It is estimated that a third of the insects attracted to artificial light die from collisions, burn injuries, exhaustion, and/or predation (7). In the tropics, finding countless dead insects at the base of urban lights is a common scene. Equally important is that artificial light also hinders migration, foraging, and the search for mates in many nocturnal species (1, 8, 9).

Nocturnal jewels

Camacho and collaborators evaluated the effect of artificial lighting at night on the Chocó golden scarab (Chrysina argenteola) (10). This species inhabits the tropical rainforests of the Western Andes from Ecuador to Colombia, and is a member of the group known as ‘jewel scarabs‘ due to their metallic body coloration (11). Because of its nocturnal habits and the larvae’s dependence on wood for food (12), the golden scarab has been increasingly affected by the loss of native forest in combination with light pollution from rural and urban expansion.

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Categories : agriculture, behaviour, conservation, decline, deforestation, ecology, extinction, fragmentation, habitat loss, rain forests, research, South America, tropical

New job posting: Research Fellow in Eco-Epidemiology & Human Ecology

11 05 2023

We are currently seeking a Research Fellow in Eco-epidemiology/Human Ecology to join our team at Flinders University.

The successful candidate will develop spatial eco-epidemiological models for the populations of Indigenous Australians exposed to novel diseases upon contact with the first European settlers in the 18th Century. The candidate will focus on:

  • developing code to model how various diseases spread through and modified the demography of the Indigenous population after first contact with Europeans;
  • contributing to the research project by working collaboratively with the research team to deliver key project milestones;
  • independently contributing to ethical, high-quality, and innovative research and evaluation through activities such as scholarship, publishing in recognised, high-quality journals and assisting the preparation and submission of bids for external research funding; and
  • supervising of Honours and postgraduate research projects.


The ideal candidate will have advanced capacity to develop eco-epidemiological models that expand on the extensive human demographic models already developed under the auspices of the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, of which Flinders is the Modelling Node. To be successful in this role, the candidate will demonstrate experience in coding advanced spatial models including demography, epidemiology, and ecology. The successful candidate will also demonstrate:

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Categories : Australia, behaviour, connectivity, demography, disease, ecology, environmental science, health, modelling, palaeo-ecology, population dynamics, research, science, societies

Bane of the bees

19 04 2022

Bees are essential for pollination, but their critical function can be perturbed by pesticides. The detrimental effects of those chemicals accumulate through a bee’s life, and become stronger if females cannot collect pollen from wildflowers.

Our childhood experiences partly determine our health, personality, and lifestyle when we are adults, and our experiences accumulate over time. Accumulation also occurs in any living being and can explain why some populations and species adapt to their environments better than others.

Migratory birds are a clear example. Thousands can travel to their breeding grounds after wintering elsewhere, and those coming from regions laden with resources (e.g., food, shelter, water) will have a greater reproductive success than those that migrated from resource-poor regions (1). In ecology, these ‘carry-over’ effects can take place between seasons, but also across the different phases of the life cycle of a plant or animal (2).

From larvae to adults

Clara Stuligross and Neal Williams have studied the carry-over effect of pesticides on the blue orchard bee Osmia lignaria in California (3). Instead of the typical hives constructed by the honey bee (Apis mellifera), solitary blue orchard bees make lines of brood cells with mud partitions, glued into holes and crevices of branches and trunks from fallen trees (see videos here, here, & here).

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Categories : agriculture, behaviour, connectivity, conservation, conservation biology, ecology, pollination, research, toxicology, toxification

Everything you always wanted to know about conservation (but were afraid to ask)

14 05 2021

While some of us still might imagine the conservationist as a fancy explorer discovering new species in a remote corner of the world, or collecting samples while drowning in mud, a growing portion of conservation science nowadays consists of asking people about their ideas and behaviours.

Needless to say, this approach produces a fair share of awkward, if not dangerous, situations. After all, who likes the idea of completing a questionnaire from the fisheries office, asking about compliance with harvest limitations or licence fees? Or, even worse, who fancies being asked about the possession of illegally traded wildlife? 

Many conservationists would really like to have this valuable information, but at the same time it is clear that these questions put people at great discomfort. This leads to biased estimates of important behaviours affecting conservation. This is where specialised questioning techniques can help.

Specialised questioning techniques aim to prevent researchers, or anyone else, to trace back individual answers. Many do so by adding noise with a known distribution to individual answers. Then, when all answers are pooled, this noise is ruled out with statistical approaches. Noise can come from a randomising device (e.g. a die), like in the randomised response technique:

Individual answers can also be masked by asking respondents not to indicate if they engaged in a certain behaviour, but by asking them, out of a list of sensitive and non-sensitive behaviours, to indicate the number in which they engaged. This is the case of the unmatched count technique (a.k.a list experiments):

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Categories : behaviour, biodiversity, bushmeat, conservation, conservation biology, exploitation, food, harvest, human-wildlife conflict, research

How to avoid reduce the probability of being killed by a shark

31 03 2021

Easy. Don’t go swimming/surfing/snorkelling/diving in the ocean.

“Oh, shit”

Sure, that’s true, but if you’re like many Australians, the sea is not just a beautiful thing to look at from the window, it’s a way of life. Trying telling a surfer not to surf, or a diver not to dive. Good luck with that.

A few years ago, I joined a team of super-cool sharkologists led by Charlie ‘Aussie-by-way-of-Belgium shark-scientist extraordinaire‘ Huveneers, and including Maddie ‘Chomp’ Thiele and Lauren ‘Acid’ Meyer — to publish the results of some of the first experimentally tested shark deterrents.

It turns out that many of the deterrents we tested failed to show any reduction in the probability of a shark biting, with only one type of electronic deterrent showing any effect at all (~ 60% reduction).

Great. But what might that mean in terms of how many people could be saved by wearing such electronic deterrents? While the probability of being bitten by a shark is low globally, even in Australia (despite public perceptions), we wondered if the number of lives saved and injuries avoided was substantial.

In a new paper just published today in Royal Society Open Science, we attempted to answer that question.

To predict how many people could avoid shark bites if they were using properly donned electronic deterrents that demonstrate some capacity to dissuade sharks from biting, we examined the century-scale time series of shark bites on humans in Australia. This database — the ‘Australian Shark Attack File‘ — is one of the most comprehensive databases of its kind.

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Categories : Australia, behaviour, biodiversity, conservation, ecology, environmental policy, fish, human-wildlife conflict, marine, modelling, ocean, predation, predator, research, shark, water

Successful movers responding to climate change

16 06 2020

tropical fishes range shiftsEcologists often rely on measuring certain elements of a species’ characteristics, behaviour, or morphology to determine if these — what we call ‘traits’ — give them certain capacities to exploit their natural environments. While sometimes a bit arbitrarily defined, the traits that can be measured are many indeed, and sometimes they reveal rather interesting elements of a species’ resilience in the face of environmental change.

As we know, climate change is changing the way species are distributed around the planet, for the main (and highly simplified) reason that the environments in which they’ve evolved and to which they have adapted are changing.

In the simplest case, a warming climate means that there is a higher and higher chance you’ll experience temperatures that really don’t suit you that well (think of a koala or a flying fox baking in a tree when the thermometer reads +45° in the shade). Just like you seeking those nice, air-conditioned spaces on a scorcher of a day, species like to move to where conditions are more acceptable to their particular physiologies and behaviours.

When they can’t change fast enough, they go extinct.

Ecologists use life-history traits to predict which species have the highest probability of moving to new areas in response to climate change. Most studies into this phenomenon have largely ignored that range shifts in fact occur in sequential stages: (1) the species arrives in a new place for the first time, (2) its population increases in size (and extent), and (3) it can continue to persist in the new spot. Read the rest of this entry »


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Categories : alien species, Australia, behaviour, bioclimatic envelope, biogeography, climate change, climate shift, coasts, community ecology, coral reefs, ecology, ecosystem, extinction, fish, food, function, invasive species, marine, monitoring, southern Australia, tropical

Adult disguises

2 12 2019

Skilled ornithologists can tell the age of a bird by the look of its feathers. But many species are advancing the moult of their first adult plumage in response to global warming, and the youngsters look more similar to the adults now than two centuries ago.

R Graphics Output

The clothes don’t make the (wo)man, but how we dress sends out a lot of information about our tastes, emotional state, or financial situation. In nature, where species have evolved to exploit all kinds of physical and chemical cues, visual communication determines a wealth of feeding and reproductive strategies (1).

Birds are familiar to all of us by the beauty and variety of their plumages (see extreme examples commented by David Attenborough here, here and here), which bird fans use to tell juveniles from males, males from females and breeders from migrants. In evolutionary time, birds have gradually moved away from tree-bark browns and tree-leaf greens and, due to functional requirements, modern feathers only span about one third of the colours these animals can perceive (2). They obtain yellows, oranges, and reds from carotenoid-containing food, dark colours from melanin pigment of own synthesis, and the so-called structural colours depend on how light reflects on the barbs of the feathers (2).

Plumage, across its entire range of designs, is a factor crucial to the life history of our feathery friends and, consequently, to evaluate how and how much anthropogenic climate change is impacting them (3).

Plumage and temperature

We know that mammals and birds are modifying their fur and feathers to optimise camouflage against landscapes with more or less snow (4), but less-known are the implications of climate change for feather moulting. Read the rest of this entry »


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Categories : anthropocene, behaviour, biodiversity, climate change, conservation, ecology, invasive species

Penguins cheated by ecosystem change

13 03 2018

Jorge Drexler sings “… I was committed not to see what I saw, but sometimes life is more complex than what it looks like …”*. This excerpt by the Oscar-winning Uruguayan singer seems to foretell the theme of this blog: how the ecological complexity of marine ecosystems can elicit false signals to their predators. Indeed, the fidelity of marine predators to certain feeding areas can turn demographically detrimental to themselves when the amount of available food shrinks. A study of jackass penguins illustrates the phenomenon in a context of overfishing and ocean warming.

CB_JackassPenguinsEcologicalTrapPhoto

Adult of jackass penguin (Spheniscus demersus) from Robben Island (South Africa) — in the inset, one of the first juveniles released with a satellite transmitter on its back. The species is ‘Endangered’ under IUCN’s criteria (28), following a recent halving of the total population currently estimated at ~ 80,000 adults. Jackass penguins are the only penguins living in Africa, and owe their common name to their vocalisations (you can hear their braying sounds here); adults are ~ 50 cm tall and weigh ~ 3 kg. Photos courtesy of Richard Sherley.

Surface temperature, dissolved oxygen, acidity and primary productivity are, by and large, the top four environmental factors driving the functionality of marine ecosystems (1). Growing scientific evidence supports the idea that anthropogenic warming of the atmosphere and the oceans correlates with this quartet (2). For instance, marine primary productivity is enhanced by increased temperatures (3), but a warmer sea surface intensifies stratification, i.e., stacked layers of seawater with contrasting physical and chemical properties.

In coastal areas experiencing ‘upwelling’ (where winds displace surface water, allowing deep water laden with nutrients to reach the euphotic zone where plankton communities feast), stratification weakens upwelling currents and, in turn, limits the growth of plankton (4) that fuels the entire trophic web, including our fisheries. The study of these complex trophic cascades is particularly cumbersome from the perspective of large marine predators because of their capacity to move long distances, from hundreds to thousands of kilometres (5), with strong implications for their conservation (6).

With those caveats in mind, Richard Sherley and colleagues satellite-tracked the movement of 54 post-fledged, juvenile jackass penguins (Spheniscus demersus) for 2-3 years (7). All individuals had been hatched in eight colonies (accounting for 80% of the global population), and were equipped with platform terminal transmitters. Jackass penguins currently nest in 28 island and mainland locations between South Africa and Namibia. Juveniles swim up to 2000 km in search of food and, when approaching adulthood, return to their native colonies where they reproduce and reside for the remainder of their lives (watch individuals swimming here).

The natural history of this species is linked to the Southern Hemisphere’s trade winds (‘alisios’ for Spanish speakers), which blow from the southeast to the tropics. In the South Atlantic, trade winds sustain the Benguela Current, the waters of which surface from some 300 m of depth and fertilise the marine ecosystems stretching from the Western coasts of South Africa to Angola (8). Read the rest of this entry »


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Categories : Africa, behaviour, birds, climate change, climate shift, coasts, decline, ecology, ecosystem, ecosystem function, fish, fisheries, food, function, harvest, impact, research, science, trophic cascades

Microclimates: thermal shields against global warming for small herps

22 11 2017

Thermal microhabitats are often uncoupled from above-ground air temperatures. A study focused on small frogs and lizards from the Philippines demonstrates that the structural complexity of tropical forests hosts a diversity of microhabitats that can reduce the exposure of many cold-blooded animals to anthropogenic climate warming.

Luzon forest frogs

Reproductive pair of the Luzon forest frogs Platymantis luzonensis (upper left), a IUCN near-threatened species restricted to < 5000 km2 of habitat. Lower left: the yellow-stripped slender tree lizard Lipinia pulchella, a IUCN least-concerned species. Both species have body lengths < 6 cm, and are native to the tropical forests of the Philippines. Right panels, top to bottom: four microhabitats monitored by Scheffers et al. (2), namely ground vegetation, bird’s nest ferns, phytotelmata, and fallen leaves above ground level. Photos courtesy of Becca Brunner (Platymantis), Gernot Kunz (Lipinia), Stephen Zozaya (ground vegetation) and Brett Scheffers (remaining habitats).

If you have ever entered a cave or an old church, you will be familiar with its coolness even in the dog days of summer. At much finer scales, from centimetres to millimetres, this ‘cooling effect’ occurs in complex ecosystems such as those embodied by tropical forests. The fact is that the life cycle of many plant and animal species depends on the network of microhabitats (e.g., small crevices, burrows, holes) interwoven by vegetation structures, such as the leaves and roots of an orchid epiphyte hanging from a tree branch or the umbrella of leaves and branches of a thick bush.

Much modern biogeographical research addressing the effects of climate change on biodiversity is based on macroclimatic data of temperature and precipitation. Such approaches mostly ignore that microhabitats can warm up or cool down in a fashion different from that of local or regional climates, and so determine how species, particularly ectotherms, thermoregulate (1). To illustrate this phenomenon, Brett Scheffers et al. (2) measured the upper thermal limits (typically known as ‘critical thermal maxima’ or CTmax) of 15 species of frogs and lizards native to the tropical forest of Mount Banahaw, an active volcano on Luzon (The Philippines). The > 7000 islands of this archipelago harbour > 300 species of amphibians and reptiles (see video here), with > 100 occurring in Luzon (3).

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Categories : amphibian, behaviour, biodiversity, carbon, climate change, climate shift, conservation biology, decline, ecology, extinction, frog, function, research, science, threatened species, trophic cascades, tropical

Spring asynchrony in migratory birds

15 05 2017

CB_ClimateChange5_BirdLateMigratoryArrival_Photo

Brent geese flock in the Limfjorden (Denmark) – courtesy of Kevin Clausen. The Brent goose (Branta bernicla) is a migratory goose that breeds in Arctic coasts, as well as in northern Eurasia and the Americas, starting from late May to early June. Adults are about 0.5 m long, weigh some 2 kg and live up to 30 years. Their nests are placed in the ground, where reproductive pairs incubate a single clutch (≤ 5 eggs) for a couple of months. They are herbivores, feeding on algae (mainly Zostera marina in Limfjord) and seagrass in estuaries, fjords, intertidal areas and rocky beaches during fall and winter. During summer they feed on tundra herbs, moss, lichens, as well as aquatic plants in rivers and lakes. The species is ‘Least Concern’ for the IUCN, with a global population at some 600,000 individuals.

Migratory birds synchronise their travel from non-breeding to breeding quarters with the seasonal conditions optimal for reproduction. Above all, they decide when to migrate on the basis of the climate of their wintering areas while they are there. As climate change involves earlier springs in the Arctic but not in the wintering areas, there is a lack of synchronisation that leads to a demographic decline of these birds in the polar regions where they breed.

When I think about how species respond to climate change, the song from the Clash “Should I stay or should I go” comes to mind. As climate changes, species eventually have to face an ultimate choice: (i) stay and adapt to novel conditions or become locally extinct if adaptation fails, (ii) or move to other regions where climatic conditions should be more suitable. Migratory species have to face this decision every time they have to move back and forth from non-breeding to breeding grounds.

Migration is a behavioural strategy shared by different animal groups like sea turtles, mammals, amphibians, insects or birds. Species move from one area to another usually to feed and reproduce in the best climatic conditions possible. For birds, migration is a common phenomenon that typically entails large movements between breeding and wintering grounds. These vertebrates boast some of the longest migratory distances known in the animal kingdom, particularly seabirds like Artic terns, which can complete up to a round-world trip in a single migratory event between the UK and the Antarctic (1). There are several theories about the mechanisms triggering bird migration, including improving body condition and fitness through unexploited resources (2), reducing parasite load (3), minimizing predation risk (4), maximizing day-light (5), or reducing competition (6, 7). Whatever the cause, birds have to decide when the best moment to migrate is, counting only with the (usually climatic) clues they have at the departure site. Read the rest of this entry »


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Categories : behaviour, bioclimatic envelope, biodiversity, birds, climate change, climate shift, conservation, decline, ecology, evolution

Noses baffled by ocean acidification

18 04 2017

Clown fish couple (Amphiprion percula) among the tentacles of anemone Heteractis magnifica in Kimbe Bay (Papua New Guinea) – courtesy of Mark McCormick. Clownfish protect anemones from predators and parasites in exchange of shelter and food. The fish tolerates the host’s venom because its skin is protected by a mucus layer some 2-3× thicker than phylogenetically related species (12); clownfish fabricate the mucus themselves and seem to obtain anemone antigens through a period of acclimation (13), but whether protection is acquired or innate is still debated. Clownfish are highly social bony fish, forming groups with one reproductive pair (up to 11 cm in length each) and several smaller, non-reproductive males. Reproduction is protandrous (also known as sequential hermaphroditism), so larvae are born male and, as soon as the reproductive female dies, her widower becomes female and the largest of the subsidiary males becomes the alpha male. The IUCN lists clownfish, generically named ‘anemone fish’, as threatened by the pet-trade industry and habitat degradation, although surprisingly, only 1 species has been assessed (A. sandaracinos). The clown anemone fish A. ocellaris is the species that inspired Nemo in the 2003 Academy-Award fiction movie – contrary to the logical expectation that the Oscars Red Carpet would generate support for conservation on behalf of Hollywood, of the 1568 species represented in the movie, only 16 % of those evaluated are threatened (14).

Smell is like noise, the more scents we breathe in one sniff, the more difficult it is to distinguish them to the point of olfactory saturation. Experimental work with clownfish reveals that the increase in dissolved carbon dioxide in seawater, mimicking ocean acidification, alters olfactory physiology, with potential cascading effects on the demography of species.

Places such as a restaurant, a hospital or a library have a characteristic bouquet, and we can guess the emotional state of other people by their scents. Smell is critical between predators and prey of many species because both have evolved to detect each other without the aid of vision. At sea, the smell of predators dissolves in water during detection, attack, capture, and ingestion of prey, and many fishes use this information to assess the risk of ending up crunched by enemy teeth (1, 2). But predator-prey interactions can be modified by changes in the chemical composition of seawater and are therefore highly sensitive to ongoing ocean acidification (see global measuring network here). Experts regard ocean acidification as the ‘other CO2 problem’ of climate change (3) — just to emphasize that anthropogenic climate-change impacts terrestrial and aquatic ecosystems alike. Acidification occurs because the ocean absorbs CO2 at a rate proportional with the concentration of this gas in the atmosphere and, once dissolved, CO2 becomes carbonic acid (H2CO3), which in turn releases protons (H+) — in simple terms, pH is the concentration of protons (see video about ocean acidification): Read the rest of this entry »


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Categories : acidification, behaviour, biodiversity, carbon, climate change, climate shift, conservation biology, decline, demography, development, ecology, extinction, fish, function, marine, ocean, predation, predator, research, threatened species, tropical

Singin’ in the heat

9 03 2017

coqui & forest

Common coqui frog male (Eleutherodactylus coqui, snout-to vent length average ~ 3 cm) camouflaged in the fronds of an epiphyte in the El Yunque National Forest (Puerto Rico), along with an image of the enchanted forest of the Sierra de Luquillo where Narins & Meenderink did their study (4) – photos courtesy of Thomas Fletcher. This species can be found from sea level to the top of the highest peak in Puerto Rico (Cerro Punta = 1338 m). Native to mesic ecosystems, common coquis are well adapted to a terrestrial life, e.g., they lack interdigital webbing that support swimming propulsion in many amphibians, and youngsters hatch directly from the egg without transiting a tadpole stage. The IUCN catalogues the species as ‘Least Concern’ though alerts recent declines in high-altitude populations caused by chytrid fungus – lethal to amphibians at a planetary scale (9). Remarkably, the species has been introduced to Florida, Hawaii, the Dominican Republic and the Virgin Islands where it can become a pest due to high fertility rates (several >20 egg clutches/female/year).

Frog songs are species-specific and highly useful for the study of tropical communities, which host the highest amphibian diversities globally. The auditory system of females and the vocal system of males have co-evolved to facilitate reproductive encounters, but global warming might be disrupting the frequency of sound-based encounters in some species..

It is a rainy night, and Don (Gene Kelly) has just left his love, Kathy (Debbie Reynolds), at home, starting one of the most famous musical movie scenes ever: Singin’ in the rain …

Amphibians (see Amphibians for kids by National Geographic) also love to sing in rainy nights when males call for a partner, but now they have to do it in hotter conditions as local climates become warmer. Vocal behaviour is a critical trait in the life history of many frog species because it mediates recognition between individuals, including sexual selection by females (1).

With few exceptions, every species has a different and unique call, so scientists can use call features to identify species, and this trait is particularly useful in the inventory of diverse tropical communities (2). Differences in call frequency, duration and pitch, and in note, number, and repetition pattern, occur from one species to another. And even within species, songs can vary from individual to individual (as much as there are not two people with the same voice), and be tuned according to body size and environmental temperature (3). Read the rest of this entry »


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Categories : amphibian, behaviour, bioclimatic envelope, biodiversity, climate change, climate shift, decline, extinction, function, rain forests, research, South America, tropical