Predator – Prey Relationship - Wildlife Managers, Preen Your Eyes

Sometimes simple things take on an entirely new facet when you delve deep in it. This is exactly what happened when scientists took a deep scan of the predator-prey relationship with emphasis on loss of predators in an ecosystem. They have come up some facts that are akin to fiction.

It is an established fact that predators control populations of prey animals, but the latest studies show that there is much more than what meets the eye. It has come to light that apex predators also control smaller predators (mesopredators), and render invaluable ecosystem services like protecting river banks from erosion and providing nutrient hotspots.

This slew of latest information has come from the research by Euan G. Ritchie, Beschta, R.L, Bump, J.K. et al and is very germane in areas where top predators are disappearing and hold lot of portents for us in India against the backdrop of disappearance of tigers.

Where apex predators become extinct, mesopredators move to the apex and practice what apex predators were doing. In stark contrast to the skills of the apex predators the mesopredators do not possess, an identical mix of honed hunting habits and skills. This topsy-turvy situation brings in cascading effects on the ecosystem, the full implications of which are being now unraveled and it makes fascinating reading.

Researchers Euan G. Ritchie and Christopher N. Johnson have contoured two ways in which top predators impact lesser mesopredators. These factors are what they call loathing and Fear .Top predators loathe mesopredators and have a natural tendency to exterminate them. Scientists say perceived competition could be a factor that makes them seek out mesopredators and kill them. This in turn leads to reduction in the abundance of mesopredators. Fear is another key that plays key role. Studies have demonstrated that fear of apex predators can engender behavioral shifts in mesopredators. Fear may also cause mesopredators to reduce or change their times of activity and shift in their habitat preferences. This in turn can lead to the reduced ability of mesopredators to find food, directly impacting and lowering reproduction and survival.

An interesting scenario unfolds where the behavior of top predators actually aids the survival of certain prey species. By keeping a constant check on mesopredators, top predators in turn become protectors of prey species, especially smaller prey. The researchers say it won’t be outlandish to call the world’s top predators 'guardians of small prey species'.

A reduction in top predators allows mesopredators to increase disproportionately. Research indicates that sometimes this could be as much as fourfold. The mesopredators with a high reproductive rate when compared to larger predators can quickly increase in abundance and drive prey species to extinction. Even if large predators also occasionally eat the same prey species as mesopredators, their impact is lower due to their larger territories and smaller overall population sizes.

The decline or extirpation of top predators can have drastic impacts on plant community also. The removal of top predators from landscapes reduces predation and ensuing predation risk. Untrammeled foraging by large herbivores that ensues, leads to heavy utilization of plants by these animals. Over time this can alter the very composition of plant communities and thus impact other animals that are dependent upon these plants. Local extinction of certain plants is also a distinct possibility.

Scientist who did a detailed analysis of five parks in USA found that, twenty years after top predators were displaced, tree recruitment declined to 10 percent of the number required for maintaining historical tree communities. An analysis of data over a period fifty years demonstrated effects, which were even more pronounced. The recruitment levels had dropped to 1 percent. Eventually this trend would lead to local extinction of many native trees.

The decline in surviving trees and the loss of particular species of plants due to predator loss can have ripple effects on the ecosystem. Accelerated erosion of hill-slope soils or of stream banks can occur as the diversity and biomass of plant communities gets affected. The loss of top predators can also have massive impacts on aquatic environments, including altering and degrading plant communities .This could lead to a situation where the plant community may be no longer capable of maintaining stable stream banks during periods of high water flow.

One of the surprising discoveries was that through hunting, the apex predators actually create nutrient hotspots that keep ecosystems rich and varied by enriching the soil with biochemicals. The scientists found that the soils of kill-sites were 100 to 600 percent richer in inorganic nitrogen, phosphorous, and potassium than control sites. In addition the area had abundance of bacterial and fungal fatty acids also. Nitrogen levels in foliage at kill-sites were 25 to 47 percent higher than control sites.

Nature works in myriad ways. We have only scratched the surface. The cascading effect of loss of predators is one such example. This should be an eye opener for our wildlife manger.

More on Prescribed Burning

Recently I had published a blog post on prescribed burning which evoked good response. 

The other day I ran in to a good paper on effects of prescribed burning from Australia titled “Survival behaviour of swamp wallabies during prescribed burning and wildfire” 

Scientists Nathan Garvey, Dror Ben-Ami, Daniel Ramp and David B. Croft followed the movements of radio-collared peri-urban swamp wallabies during a prescribed burn and after an unexpected wildfire in the same location a short time later. 

No radio-collared swamp wallabies were killed during the prescribed burn and only one wallaby was observed to emigrate from the area post-fire. Scientist says that wallabies can avoid fire fronts and that this avoidance behaviour may be more successful during cooler fires.  This contrasted to the wildfire where one wallaby died during or just after the fire and another perished in the post-fire environment a few months later. The wildfire also increased emigration post-fire. 

The prescribed burn provided a suitable habitat for wallabies but did not result in a shift in habitat preference. They also say mitigation of the impact of prescribed burns on swamp wallabies may be achieved by allowing sufficient time for habitat complexity to re-establish between burns. 

Details can be accessed at   Wildlife Research 37(1) 1–12    doi:10.1071/WR08029

Athirapally Dam - Jairam Rameshji , Follow the Path of Ingenuity

The arguments of the people opposing Athirapally dam are totally unexceptionable. The rich biodiversity of the area cannot be bartered away for paltry megawatts of electricity. The indigenous people of the area also stand to lose considerably.  

The bold stand taken by Jairam Rameshji against the dam has endeared him to the green brigade of Kerala. At the same time we also have to step in to the shoes of the electricity people and have a look at the entire event from their perspective also. Not all of them are anti-environmentalists. Their job is to produce and distribute electricity. In their eyes there is nothing to beat hydropower when it comes to non polluting source of electricity production. It also is the cheapest source of electicity. 

So how do we come to a modus Vivendi?  If Kerala is denied the right to produce hydro electricity then the state will have to go in for very expensive thermal alternative. They will have to either produce it or buy it from outside.  

The best course for the centre would be to subsidize the difference between hydro power and thermal power and ensure uninterrupted power for the state. This way the forest is saved and the electricity people also would be a happy lot. The green bucks that bridge the gap between hydro and thermal power cost would be an incentive for the state to protect the forest. 

So Jairam Rameshji here is an opportunity for you to break new ground and as the saying goes ,kill two birds with one shot.

Moringa Tree

The fact that Moringa( Moringa oleifera) is an excellent material for water purification is known to some indigenous communities. Now there is scientific validation for the claim. I have posted an item in my other blog on this. I have also included a download link for the full paper which has been made free to download as part of access programs under John Wiley & Sons' Corporate Citizenship Initiative. Read the story here

King Cobra Charms Researchers

Scientists have been studying king cobra for the past 50 years. Latest research has thrown up some exciting possibilities. I have posted small item in my other blog. Read it here

The Sanctity of Management Plans

Last week I got an invitation from wildlife warden Munnar to attend a workshop, meant as an initiation workshop for revision of management plans for Eravikualm and Chinnar.

I was not able to make it due to prior commitments at Calicut. But at the back of my mind it kindled some disturbing thoughts.

In many wildlife reserves the plans serve as scarecrows only. It deteriorates in to a compendium of sanctimonious sermons that are rarely adhered to. I can quote umpteen incidents where the the management plans have been thrown by the way side in the pursuit of development agenda.

A quick look at the works taken up in wildlife reserves makes you wonder whether the concerned people have ever read the management plans. I am sure they never had a look at it. It is gathering dust somewhere in the recesses of the office.

A wildlife management plan is a sacred document. To many, the word sacred may be a wee bit unpalatable. But I strongly feel no other word can replace the true spirit behind it.  wildlife management plans should be the bible for the wildlife manger. This is particularly so when we have uninitiated dilettante who have no formal wildlife training managing the wildlife reserves.  I do not want to mince my words here and would like to state what is obvious. If we cannot adhere to the management plans there is no use spending time and money on preparing management plans. You could very well do with a hastily patched up yearly plan.

In Defense of Prescribed Cool Burning

Prescribed burning has always been a controversial subject. The subject is going to be the epicenter of heated discussions in the days to come as the revision of management plan of Eravikulam National Park is on its way. I have always been an unabashed votary of prescribed cool burning.  The latest research buttresses my arguments.  As scientists gather more and more information on the effects of fire on forest ecosystems, they have learned that fire exclusion may not be the best practice for land management.  There is increased awareness that a forest fire is part of the overall ecology and is part of the overall balance despite earlier fears that forest fires were only deleterious. Not only does fire exclusion cause an accumulation of thick vegetation on the forest floor, but also causes and increased density of smaller trees. A fire in a forest that has been excluded from fires for many years is disastrous and pushes back all the good work by many years. The fire becomes a holocaust.  The blaze burns at a much higher intensity causing more damage to the forest ecosystem. On a long-term basis particularly in a thickly populated state like Kerala fire will be an inevitable part of forest ecosystems. So why not manage and mitigate the effects instead of living in a fool’s paradise.

Many people have concerns that prescribed fires affect animals in a negative way.  The fire itself does not harm the animals for several reasons. The prescribed burns are done in pre-designated patches. Most prescribed burns travel at a slow rate of less than 2 Km per hour giving most insects and animals time to leave the area or burrow deep into the ground.  Only 290 animals were found dead as a result of the Yellowstone fires in 1988, and this fire was uncontrollable and burned at very high intensities. Most prescribed fires occur when animals are not nesting or caring for their young. 

Forests that have not had a fire in decades may become the home to a plant species that is not adapted or dependent on fire.  Plants that are adapted for wildfire usually have a thick layer of bark to protect its living tissue from the heat.  Also, many trees are dependent on the heat of fire in order to open up their seed cones for regeneration.  Vegetation modification also affects the ecosystem’s insects and diseases, wildlife populations, soil structure, and nutrient recycling.

Recent ecological research has shown that forest fire is an integral component to the function and biodiversity of many ecological communities, and that the organisms within those communities have adapted to withstand and even exploit it. A fire may destroy one ecological community but allow greater long term diversity. It is not just the fire but the smoke also plays a very important role in the ecological processes. Smoke plays a prominent role in promoting the germination of seeds of many species following a fire. Even the carbon dioxide from a fire has an impact on the overall ecosystem.

Fire create a mosaic of different habitat patches, with sites ranging from just burned to untouched by fire for years, through a process known as succession. Succession is the progress of a site through continuous and directional phases of colonization by and extinction of species populations after a disturbance, such as fire.

In a recent study published in the Journal of Natural Products it was reported that a chemical compound in smoke from burning plants promotes seed germination. Such seeds, which remain in the undercover on forest and meadow floors after fires have been extinguished, are responsible for the surprisingly rapid regrowth of fire devastated landscapes.

In their research, the scientists report discovery of an inhibitor compound that may block the action of the stimulator, preventing germination of seeds. They suspect that the compounds may be part of a carefully crafted natural regulatory system for repopulating fire ravaged landscapes. Interaction of these and other compounds may ensure that seeds remain dormant until environmental conditions are best for germination. The inhibitor thus may delay germination of seeds until moisture and temperature are right, and then take a back seat to the germination promoter in smoke.

A recent study at Oregon State University indicates that some past approaches to calculating the impacts of forest fires have grossly overestimated the number of live trees that burn up and the amount of carbon dioxide released into the atmosphere as a result. A forest fire does not cause a complete destruction or release of carbon dioxide to the atmosphere as compared to the deliberate combustion of fossil fuels.

The past estimates of fire severity and the amounts of carbon release have often been high and probably overestimated in many cases, said Beverly Law, a professor of forest ecosystems and society at OSU. Even when a very severe fire kills almost all of the trees in a patch, the scientists said, the trees are still standing and only drop to the forest floor, decay, and release their carbon content very slowly over several decades. Grasses and shrubs quickly grow back after high-severity fires, offsetting some of the carbon release from the dead and decaying trees. Abundant tree regeneration will result in a relatively fast recovery of carbon uptake and storage.

More and more government agencies such as the National Parks Service and the USDA Forest Service are adopting prescribed fire plans. Although not all of the long term effects of prescribed fires are known, most evidence shows that a prescribed fire plan’s benefits outweigh a fire exclusion plan’s benefits.

In Eravikulam National Park prescribed cool burning has been practiced right from the British days. The ecosystem has stabilized around this practice. Tinkering with the practice is fraught with unseen dangers. In Eravikualm the recruitment of Nilgiri tahr has come down to about 5 % from the 10 to 20% that was there 30 years back. I have a sneaking doubt that tinkering with the burning regime has a role in it. Only detailed research can prove it. Other possibility is disturbance. Caughly has conclusively proved that disturbances even in the absence of  poaching bring about energetic demands on the animals affecting parturition.

Opponents of prescribed burning should read the book "Yellowstone in the Afterglow: Lessons from the Fire." Yellowstone has played a critical role in demonstrating the changes brought by fires. "The lessons of '88 in the park are like classic Led Zeppelin," says Mr. Renkin, a park ecologist. "They'll be around forever."

Have a look at the other recent papers on forest fires that are available on the net.