Threats to frogs...
Around 33% of all the world’s frog species are threatened with extinction! Many other frog species could also be in serious decline, as many species have not yet been properly assessed. For some frogs it is already too late, as several species have already gone extinct! Below is an outline of the threats that frogs face.
One the biggest reasons that frogs are disappearing is their habitats (i.e their homes) are being destroyed. Many areas that were once suitable for frogs to live have now been demolished for developmental construction and agriculture. Habitats of all kinds are being lost at an alarming rate. Wetlands are drained, forests are logged and cut down, and waterfronts are developed. Frogs are literally losing their homes and they are losing them rapidly! Deforestation is particularly harmful to frogs. When the amount of shade that covers the forest floor is reduced due to the removal of trees, the increased sunlight can allow for higher temperatures to reach the forest floor. This exposed sunlight can also rapidly dry up temporary flooded areas (called vernal pools) on the forest floor which are crucial breeding/birthing sites for many frog species. The expansion of urban areas threatens the suitable habitats that still remain.
Where natural habitats do still exist, they are often cut off from one another or degraded. Fragmentation occurs when healthy areas of habitat are isolated from one another. These fragmented areas are known as habitat islands. Frog populations are affected since gene flow between the populations is prevented.
This increases the occurrence of inbreeding, which results in a decrease in genetic variability and the birthing of weaker individuals. Fragmented populations where inbreeding occurs often ends in a genetic bottleneck. This is an evolutionary event where a significant percentage of the population or species is killed or otherwise prevented from reproducing. Habitat fragmentation is also harmful because it often eliminates crucial requirements in the area which are critical to the survival of frog populations.
Such areas include spaces that can be utilized for thermoregulation, prey capture, breeding, and over-wintering. Without such habitat requirements populations dwindle. Breeding sites, often in the forms of vernal pools are particularly important. The loss of such areas in the form of habitat destruction can negatively affect the entire population and its reproductive output.
Degradation occurs when the natural habitat has been altered and degraded to such a degree that it is unlikely that any remaining frog species would be able to survive. Developments and agriculture near fragmented habitats put frogs at serious risk. As amphibians, frogs have extremely absorbent skins. Industrial contaminants, the introduction of sedimentation into waterways, sewage run off, pesticides, oils, and other chemicals and toxic substances from developmental construction sites and human settlements can all be absorbed by frogs. This can quickly lead to deaths. They can also cause widespread horrific deformities to occur.
Habitat destruction and degradation can also effect the availability of prey items, causing unnatural declines in appropriate food sources.
Habitats are often isolated and cut off from one another by the roads and highways that now run through them. Countless numbers of frogs are killed on roads and highways every year when they are hit by vehicles. Frogs that are migrating to breeding and egg-laying sites often must cross over roads to reach such areas. Here many of the mature members of the breeding population are killed. Removing members of the breeding populations greatly limits reproductive output, this makes it incredibly hard for frog numbers to rebound.
Roads present an additional problem because they represent a form of habitat loss. The roads that run through natural areas also fragment the existing populations, drastically making them smaller in size. This limits the gene flow and genetic diversity between the isolated populations on either side and this greatly increases the chances of extirpation. When frogs attempt to cross roads to travel between the populations, or to critical breeding/birthing sites it greatly increases their chances of being hit and killed by vehicles.
In 2006, researchers from Carleton University surveyed 38 ponds for frogs in rural areas. They also recorded the amount of intact forest and wetland within 2 kilometres of the ponds, and the volume of road traffic in the areas. They found that heavy traffic was a negative pressure for the amphibians, and for five out of six frog species recorded, it reduced populations even more than the loss of their habitat! Therefore, reducing road mortality is paramount to preserving frog species.
Being hit and killed by vehicles is not the only threat that roads create for frogs. Chemical run-off from vehicles contaminate roadside ditches and pools. These sites are often utilized by frogs for breeding and birthing.
Poaching/Taking From The Wild
Millions of frogs are captured from their natural habitats every year. Legions of Frogs are taken from the wild to be sent off to the exotic pet trade. The wild-caught pet trade severely depletes already at-risk wild populations. Over 20 million wild-caught amphibians are sold every year in the U.S. alone. Frogs are also captured in huge numbers to be used for food and for use in the fishing bait trade.
The practice of using frogs as bait is extremely cruel. Frogs are vertebrate animals that are sentient beings (just like dogs and cats), and are fully capable of experiencing pain and suffering. This is known through the presence of nociceptors and a Central Nervous System (CNS), and the connection of nociceptors to the CNS. Furthermore, according to L.K. Machin (1999 & 2001), amphibians have shown behavioral responses to pain, and have shown responses to pain-killers. The ability for frogs to experience pain and suffering is an important message to note when considering the conservation and cruelty concerns that these animals often face. As such, stabbing live frogs with hooks for use as fishing bait is extremely cruel.
For more information on frogs as bait, click here.
Chytridiomycosis is an often fatal infectious skin disease that seriously affects amphibians. The condition is caused by the chytrid fungus (Batrachochytrium dendrobatidis) Chytrid has been responsible for mass declines in frog populations. Devastatingly, it has been found on all of the continents where frogs occur. It may be responsible for the greatest disease-caused loss of biodiversity in recorded history (Skerratt et al. 2007)!
Sadly, Chytrid is not the only disease causing mass die-offs of frogs. Ranavirus is another ailment that is impacting frogs negatively. The pathogen causes severe hemorrhages of the internal organs.
The serious amphibian diseases ranaviruses and chytrid fungus are also being spread throughout populations and to previously healthy animals via the fishing bait trade. When infected animals are captured from the wild for this trade, and then shipped and sold in other locations, they bring the diseases with them contaminating new areas.
Find out how you can stop the spread of frog diseases here.
Frogs are often used for dissections. In fact, dissection continues today as much as (if not more than) it did 50 years ago (Hart, Wood, & Hart, 2008). Globally, the number of amphibians used in classroom dissections is unknown; however, the Johns Hopkins University Center for Alternatives to Animal Testing has estimated that 6 million vertebrate animals are dissected in U.S. high schools each year, well over half of which are believed to be amphibians. Using frogs for dissections is both an animal cruelty and conservation issue. It is also unnecessary. Animals used for dissections are predominantly taken from the wild. This further contributes to the decline in frogs and other amphibians. The harvesting of amphibians from the wild also upsets the balance of local ecosystems.
Furthermore, it is not just the harvesting of live animals that is cause for concern. The preservation and discarding of dead animal specimens in classrooms carries additional environmental risks. Toxic chemicals such as formaldehyde or formalin preserve millions of animals each year. The Environmental Protection Agency has designated formaldehyde as “a hazardous air pollutant, water pollutant, and waste constituent.” The scope of the toxic-chemical waste generated by the disposal of dissection specimens makes the practice a serious threat for the environment and various natural habitats. When amphibians are harvested they get moved via humans from one location to another. This action, compounded with the risk of escaped captives after capture, spreads infectious diseases from one population to another. This could also introduce disease to previously healthy populations. Captive-reared amphibians also often carry disease, if they escape they too pose the risk of spreading infection. The moving of animals from one population to another can also be a way for invasive species to be introduced into non-native ecosystems. Dr. Whit Gibbons and ten coauthors of a study in Bioscience identified six principal threats contributing to the decline in reptiles/amphibians. The study listed the introduction of invasive species (which can happen via the trade in dissection animals) as the most serious of threats aside from the destruction and degradation of natural habitat.
Not only are dissections damaging to the environment and a conservation concern, but they are also an issue of animal cruelty! According to the New England Anti-Vivisection Society, amphibians captured for dissection can be shipped live, often crammed in small cages, with no temperature regulation, food, or water. Common methods of killing of animals for dissection include suffocation, drowning, electrocution, gas chambers, or euthanasia. Past undercover video footage of supply companies has exposed that some animals are still alive as they are pumped full of formaldehyde or other preservatives. The U.S Animal Welfare Act does not include ”cold-blooded animals”, and therefore, frogs have no federal protection. Even captive-reared species are unethical, as the animals are raised solely to be killed. This is especially sad as many alternatives to dissection exists. These include computerized virtual dissections, anatomical models, films, websites, and plastinated specimens. According to Marge Peppercorn, a Harvard-trained physician, “Comparative studies have shown time and again that alternatives to dissection, from computer programs to models that are more realistic than formalin-fixed ‘specimens’- are as educationally effective, and in most cases more so, than animal dissection.
If medical and veterinary schools are rapidly replacing animals with alternatives, why shouldn’t this also be happening at the high school level?” Furthermore, dissections are also insignificant to these alternatives as deceased specimens show dead organs which are often distorted. As such they do not display body function or complex systems. The annual purchase of dissection specimens is also costly, and this depletes funds for other education needs.
Help stop frog dissections here.
Climate change is among the most serious threats that frog populations face. Detrimental changes in climate such as increased temperatures, changing humidity levels, desertification, and droughts wreak havoc on frogs. These animals are generally adapted to moist and cooler habitats and may require very specific conditions to thrive; therefore, changes to these conditions via climate change can be life threatening to frogs.
Frogs also live a ”double-life” being associated with both aquatic and terrestrial habitats. Alterations to these optimal conditions result in frog species dwindling. Changes in climate can also effect the forming and availability of critical habitat features such as vernal pools (that are utilized for breeding and birthing/egg-laying sites). Certain frog species have small natural ranges, and within these ranges show fidelity to over-wintering sites. Thus, these forms have limited opportunities for dispersal if their habitats are degraded due to negative climate changes. Climate change is often cited to be one of the reasons that frogs are disappearing from otherwise pristine and protected habitats.