Threats to Turtles

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Turtles have proved that they are one of time's most successful and resilient survivors. They have been on the Earth for well over 220 million years, and have managed to persevere throughout the ages, while countless other species have disappeared around them.

However, now turtles are very much in peril. Over half of all the world's turtle species are in need of conservation. Around 70% of the world's turtles are listed on The World Conservation Union's Redlist of threatened species.

For some turtles it is already too late, several species have already gone extinct. Many more species are being pushed to the very brink of extinction. For many individuals the term endangered species conjures up images of exotic animals found in far away lands. However, the decline and endangerment of turtles, can be seen around the world.

The issues that plague turtles are not just exclusive to species found in the wild. Every year literally millions of turtles are unwillingly forced into or reared in captive settings. Here they are subjected to many forms of abuse and cruelty, while others are exploited like commodities for monetary gain.

Below is an overview of the threats that turtles face.

Habitat Loss

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One of the biggest issues impacting turtles is the loss of their natural habitats. Many areas that were once suitable for turtles to live have now been destroyed for developmental construction and agriculture. Habitats of all kinds are being lost at an alarming rate. Wetlands are drained, forests are cut down, and waterfronts are developed. Turtles are literally losing their homes and they are losing them rapidly.

Remaining natural habitats are often fragmented or degraded.

Fragmentation occurs when healthy areas of habitat are isolated from one another. Turtle populations are affected since gene flow between populations is prevented. Habitat fragmentation is also harmful because it often eliminates crucial requirements of the area which are critical to the survival of turtle populations. Such areas include spaces that can be utilized for basking, prey capture, mating, nesting, and over-wintering. Without such habitat requirements, populations dwindle. Nesting sites are particularly important as many turtles will often use the same area year after year. The loss of such areas in the form of habitat destruction can negatively affect the entire population and its reproductive output. Habitat complexity is also important as it offers shelter to turtles from both predators and human persecution.

Habitat Degradation & Pollution

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Degradation occurs when the natural habitat has been altered and degraded to such a degree, that it is unlikely that any remaining turtle species would be able to survive.

Waterfront developments restrict turtles from prime basking and nesting sites. These developments may also cause water levels to rise which can drown any remaining turtle nests (or nest sites). Contaminants and sewage run off from developmental construction and human settlements further causes harm to turtles and their increasingly degraded habitats. Pesticides, oils, chemicals, and industrial pollution contaminate the habitats of turtles and their local prey. When the turtles consume contaminated prey, they may become poisoned and die. Noxious elements in the polluted waters can also kill turtles.

Habitat destruction and degradation can also effect the availability of prey items, causing unnatural declines in appropriate food sources.

Turtle habitats are often subjected to human-induced alterations. The introduction of erosion netting or similar netting materials such as nylon netting, plastic bird netting, chicken wire, glue traps, and garden traps can all pose serious risks to turtles. These foreign objects act as barriers, preventing turtles from migrating throughout their natural ranges. Turtles can also end up seriously injured or even killed as a result of being entangled inside such materials. Similar incidences can arise when turtles become trapped in twine, discarded netting, fishing lines, and plastic garbage. Ingesting plastic waste also threatens turtles.

Land Dominion

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The increase in human activities and recreation in natural areas, on the water, and on beaches impacts turtles and their nests in many negative ways. Turtles are often killed or severely injured when they are hit by boats or water vehicles. Nets of many varieties, end up trapping legions of turtles.

Driving on beaches with cars and four wheelers can destroy turtle nests laid in the sand or soft soil (they may also kill turtles directly, when they are run over). Beach goers often scare female turtles away from nesting sites, causing them to abandon reproductive activities.

When baby turtles hatch from their nests they will often head for the water, being led their by the natural light on the horizon. Waterfront developments create unnatural lights that lead turtles away from the safety of the water and into dangerous urbanized settings. Here they are at risk of being poached, captured by predators, or killed on roads. Those that do head for the water may get deterred by or trapped in beach furniture and other unnatural hurdles. Sand castles, sand pits, beach fires, also act as traps or hurdles for nesting turtles and their hatchlings.

 

Road kills (Traffic Mortality)

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Habitats are often isolated and cut off from one another by the roads and highways that now run through them. Countless numbers of turtles are killed on roads every year when they are hit by vehicles. In many cases, people will purposely swerve to run over and kill turtles. Traffic mortality is an extremely significant threat to turtles as it is often the mature females that are killed. This usually happens  when they are searching for nesting sites. Turtles are long-lived animals that take many years to reach maturity and thus contribute to the reproductive output of the population. When mature females are killed it removes this contributing member. However, as the eggs are usually destroyed too, vehicles not only kill the mature females but the next generation of turtles as well.

Roads that cut through areas that are rich in turtle species can quickly cause serious declines. According to the Society for Conservation Biology roads threaten both land turtles and large pond turtles: in many regions more than 5% of these turtles are likely to die while crossing roads, which is more than the populations can sustain. Studies have shown that most turtle species cannot withstand death rate increases of more than 2-3%.

Roads present an additional problem for turtles 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 turtles cross roads to travel between the populations, it greatly increases their chances of being hit and killed by vehicles.

Lawn & Field Mowing

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Terrestrial habitats such as grasslands and hayfields are home to several turtle species. These includes the Wood Turtle (Glyptemys insculpta) and Eastern Box Turtle (Terrapene carolina carolina). Both of these species are suffering from serious declines throughout their ranges. Semi-aquatic turtle species may also linger in fields, grasslands, and yards as they travel to nesting sites or other habitats. They may also utilize these areas to bask in the sun. Unfortunately, many turtles get killed by lawn mowers and plows in these habitats. According to the Massachusetts Division of Fisheries and Wildlife, mowing during the spring and summer months can cause significant turtle mortality; up to 10% of a western Massachusetts population of Wood Turtles was killed due to this (Jones 2007). In fact, researchers in rural areas are finding that the percent of mortality due to mowing and agricultural machinery is much higher than the mortality rate due to roads.

Surplus Predators

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While human activities have had negative impacts on turtles, they have helped increase a number of turtle predators. The constant supply of human waste (i.e garbage), has provided an unlimited food source for predators like skunks and raccoons. This has caused the number of these predators to increase significantly, and this surplus of predators takes a serious toll on turtle populations. These predators are especially keen on destroying turtle nests, eating the eggs. The overabundance of predators will often destroy as much as 80% of all turtle nests.

Bycatch (Incidental Catch)

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Many aquatic and sea turtles fall victim to being trapped inside nets, trawls, and lines that are intended to catch other prey. Long line fishing and shrimp nets are particularly lethal to turtles. A study conducted by Duke University scientists, found that more than 250,000 Loggerhead and 60,000 Leatherback turtles are inadvertently snared each year by commercial long line fishing, with bycatch being particularly common in the Pacific Ocean. The loggerhead turtle is listed as Endangered, while the Leatherback is designated as Critically Endangered. This loss of more then 300,000 turtles only represents two species! Many more species of both fresh-water and marine turtles are caught and killed every year in nets.

Poaching

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Every year literally millions of turtles are harvested directly from the wild so they can be sent off to food markets and for use in other trades. Turtles are captured for the pet trade, for use as food, for use in the ornament trade, and for use in traditional medicines. This wide scale harvesting of turtles takes a tremendous toll on natural populations, which are already severely strained from numerous other threats. In many parts of the world turtle meat is considered a delicacy, and the consumption of turtles is widespread and common.  Turtle eggs are also harvested and consumed in staggering numbers. The fat from turtles is used in many cosmetics. Turtles are also commonly killed and used in traditional Chinese medicines. Taiwan alone imports hundreds of tons of plastrons (bottom-shell) every year for use in medicines.

Direct/Intentional Killings

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Aside from being poached and killed for several trades and markets, many turtles are also intentionally killed by individual people. Shooting basking turtles on logs is a popular 'sport' in the Southern United States. In fact, an internet search on ''shooting turtles'' will yield numerous results including videos and discussions on forums. Turtles are also killed by fisherman who believe the misconception that turtles negatively effect fish and waterfowl populations. Snapping turtles are also often killed due to the false belief that they may attack or injure swimmers.

Climate Change

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The gender of most turtle species, is determined by environmental factors. Nests that are subjected to slightly cooler temperatures will produce predominately males. Warmer temperatures will produce females. Most clutches have temperature variations among the eggs (i.e as heat rises and other variables go to work, it creates gradients). Ideally these produce a mix of both males and females. The dependence of turtle gender determination on environmental factors means turtles are very sensitive to the threat of climate change. According to the United States Geological Survey and the University of California's Department of Biology, some scientists have suggested that global climate change has the potential to eliminate the production of male turtle offspring if mean global temperatures increase 4° C, and increases of less than 2° C may dramatically skew sex ratios. This could seriously decrease the reproductive output of turtles.

Climate change could also affect turtles in other very serious ways. Researchers from the University of Queensland found that young Mary River Turtles (Elusor macrurus) which developed under higher temperatures showed reduced swimming ability and a preference for shallower waters. This combination of physiological and behavioral effects can have dual consequences for survival chances. "Deeper water not only provides the young turtles with protection from predators but is also where their food supply is found," states PhD researcher, Mariana Micheli-Campbell. "Young turtles with poor swimming abilities which linger near the surface are unable to feed and are very likely to get picked off by birds.''

Rising sea levels due to climate change can also submerge critical areas within turtle habitats. These include basking sites, egg-laying spots, and forging areas for young turtles.

Conclusion

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A massive number of turtles are being lost each year through the combination of the many threats mentioned above. This unnatural decline in turtle populations cannot rebound on its own. This is why the conservation of many turtle species is required. Without assistance, many species simply cannot continue to survive the many hazards we have created for them.

There is much about turtles that scientists do not know. Aspects of the biology, ecology, and lifestyles of many species is a mystery. This undoubtedly means human interference is negatively impacting turtles in ways in which we don't even know. The intricate relation between all species and the vital roles they play within Eco-systems is also being altered. Such alterations can have serious consequences to not just turtles, but many other animals as well (including humans). This alone makes the conservation of turtles extremely important. However, it is most important as turtles are intrinsically valuable.