The Golden Toad

The Golden Toad have become extinct only recently, however they did not go extinct as a result of poaching or hunting by humans. It is most likely that their extinction is due to change in the climate. The Golden Toad was observed meeting annually in groups over 1500 to mate from at least 1972 when at a preserve discovered in Monteverde, Costa Rica. Scientists were able to observe the Golden Toad annually during these meetings, however in 1988 and 1989, only one toad appeared at the sight and a few more 4km South East. Then, in the years following, no toads were to be found at any location. They are classed as extinct as there have been no sightings of the Golden Toad since the late 80’s (Pounds & Crump, 1994). That is an extremely quick decline in numbers, from finding over 1500 toads in a single spot one year then none only a few years later means that an event or a rapid change in climate has affected the adults of the population significantly for them to not be returning to breed.

The Golden Toad

Photo Source: http://www.bagheera.com/inthewild/van_anim_gldtoad.htm

There are several hypotheses as to what happened to the Golden Toad. Some believe that they are hiding in reserves waiting for a change in climate to mate again (Crump, Hensley, & Clark, 1992), however this hypothesis is believed to be invalid due to the fact that the life span of the golden toad averages around 10-12 years, impossible for them to be still hiding due to the fact their last appearance was in 1989 (Pounds & Crump, 1994).

Amphibians vary in the ways in which they hydrate, however it is most common for toads to hydrate by absorbing moisture through their skin. They are often observed laying on wet surfaces such as wet rocks, logs and soil. The way for them to control their body temperature is through evaporative cooling, resulting in them losing water. Groundwater sources are the most common source for the toad to hydrate from, as their permeable skin allows them to hydrate from soil and tree roots. However the amount of ground water in a region is highly dependent on the seasons’ temperature and the amount of precipitation (Pounds & Crump, 1994).

El Nino came into play over Costa Rica in 1986-1987 which lasted a whole July-June cycle. All over the Monteverde region, El Nino affected the precipitation levels to be at an all-time low, and in turn a record low of stream discharge. In comparison to the 1982-83 El Nino, this one had unusually low precipitation levels. The seasons of the year in which the toads depended on for precipitation were very weak, and the dry season was extremely harsh, and furthermore, the temperature did not decrease after (Zhang & Endoh, 1994). Data gathered suggested also that at the time in the year when streams were being replenished, the groundwater level was continuing to drop. The warm, dry environment of meant that the breeding pools were dried up, and as a result the eggs and tadpoles all died (Pounds & Crump, 1994). The non-return of the toads the following year however is not dependent fully on the death of the young as proved by their average life span being around 10-12 years.

It is thought to most likely be the dehydration which was the main cause of the extinction, but there are several other hypotheses such as acidification of waterways due to human activity – although the pH of the waterways did not change dramatically throughout that period, human activity is not ruled out. Parasites are also a possibility as they have been the cause of extinction to many other amphibian species (Pounds & Crump, 1994). These hypotheses however are yet to be fully investigated.

The extinction of the Golden Toad goes to show how much the weather system can change over a short period. In this instance, should the hypothesis that dehydration was the main cause of extinction, it goes to show how weather can rapidly effect important resources. In the case of the Golden Toad, this resource is water. In the case of humans, the resources we need to survive are food and water, two resources which are extremely easily influenced by the climate. We are lucky in the sense that we have technology able to access water and alter it for us to consume. However as temperatures rise, the environment in which crops are growing is forever changing. The soil is being damaged, becoming less and less resourceful. While in other cases which I have investigated, the main cause of extinction was the lack of ability to adapt to an environment, the main issue here was the change in the amount of crucial resource – water. Humans should be concerned about the rise in temperature and how this is affecting the resources we need in which to survive. Not only are we dealing with the population nearing carrying capacity, we are also being faced with the issue of vegetation not being able to grow in locations they used to as a result of the temperature rising and effecting soils and on top of that, water limitations.  

References

Crump, M. L., Hensley, F., & Clark, K. (1992). Apparent Decline of the Golden Toad: Underground or Extinct? N/A: American Society of Ichthyologists and Herpetologists (ASIH).

Pounds, J., & Crump, M. (1994). Amphibian Declines and Climate Disturbance: The Case of the Golden Toad and the Harlequin. N/A: Blackwell Publishing for Society of Conservation Biology.

Zhang, R.-H., & Endoh, M. (1994). Simulation of the 1986–1987 El Niño and 1988 La Niña events with a free surface tropical Pacific Ocean general circulation model. Journal of Geophysical Research, 7743–7759.