1 Tahrcountry Musings: April 2011

Saturday, April 30, 2011

An insight in to wallowing in pigs

Review of wallowing in pigs: Description of the behaviour and its motivational basis
 M.B.M. Bracke
Volume 132, Issues 1-2, June 2011, Pages 1-13 
 In this paper researcher Dr Marc Bracke from Wageningen University and Research Centre has reviewed the wallowing in pigs and related species. The behaviour is described and it’s motivational basis is examined.

48 papers were identified containing citations about wallowing behaviour in pigs and wild boar. 12 papers contained citations about wallowing in related species
The researchers conclude that wallowing is vital for the animals' well-being.
Dr Bracke says Pigs are genetically related to particularly water-loving animals such as hippos and whales and it seems that this preference to be in shallow water could have been a turning point in the evolution of whales from land-dwelling mammals.

The common perception is that pigs wallow mainly for cooling, sunburn protection and the removal of ecto-parasites. Dr Brake says little scientific evidence exists for other functions other than thermoregulation.

Dre Brake sign off saying “Pigs lack functional sweat glands and wallowing in mud is an effective behavioural control mechanism in pigs to prevent hyperthermia. Wallowing, however, may also serve other functions, e.g. in scent-marking and sexual behaviour. In addition, wallowing in pigs, like dustbathing in poultry, may be indicative of positive welfare and, perhaps, the performance of the behaviour is ‘hardwired’ and rewarding in itself. If so, wallowing could be an important element of a good life in pigs.”

Friday, April 29, 2011

Ecosystem collapse- The importance of regular monitoring

I was fascinated to read in today’s Science daily about ecosystem collapse and how regular monitoring can be used to predict the collapses.

An experiment in Peter Lake, in Wisconsin, US headed by Dr Stephen Carpenter has come up with the finding that ecosystem collapses could be predicted with the right type of monitoring. 

Researchers changed the structure of the food web in Peter Lake, by introducing a predatory fish.
In the food web of the lake insects such as fleas ate tiny water-borne plants, small fish such as golden shiners ate the fleas, and much bigger largemouth bass ate the little fish.
In a matter of three years, the introduced fish was running all over the place. This produced a decline in tiny water plants and an explosion of water fleas.
Sensing the threat from the new predators, the golden shiners of the lake began to spend more time in the shallows. They also went in for shelter under floating logs. Larger fleas moved in and started eating the phytoplankton. Wildly varying numbers of fleas and phytoplankton were seen at different times.
After a series of flip flops by late 2010, the ecosystem appeared to have stabilised its transition from one stable state to another.

The researchers say the change was preceded by signals that could be used to predict similar collapses elsewhere. This is the first time that this phenomenon has been demonstrated experimentally.
The researchers add that that isolating these signals from the ecosystem is not only useful for predicting environmental catastrophes, but they can also be used to determine which habitats are most likely to respond to conservation

Thursday, April 28, 2011

Traffic noise and its effect on the foraging efficiency in acoustic predators

Hunting at the highway: traffic noise reduces foraging efficiency in acoustic predators
Published online before print November 17, 2010, doi:10.1098/rspb.2010.2262Proc. R. Soc. B 7 June 2011 vol. 278 no. 17121646-1652

The effects of noise on animal communication are well documented, but our knowledge is very limited when it comes to the impact of noise on more complex ecosystem processes, such as predator–prey interactions.

In this paper the researchers show that traffic noise decreases the foraging efficiency of an acoustic predator, the greater mouse-eared bat (Myotis myotis). These bats feed on large, ground-running arthropods that they find by listening to their faint rustling sounds. The researchers measured the bats' foraging performance on a continuous scale of acoustically simulated highway distances.

Successful foraging bouts decreased and search time drastically increased with proximity to the highway. At 7.5 m to the road, search time was increased by a factor of five. The researchers conclude that as most of the bats' preys are predators themselves, the noise impact on the bats' foraging performance will have cascading effects on the food web which in turn will impact the ecosystem stability. These findings apply to other ecologically important acoustic predators like owls. The study provides the empirical basis for quantitative predictions of anthropogenic noise impacts on ecosystem processes.

The researchers sign off saying that that an understanding of the effects of noise emissions and other forms of ‘sensory pollution’ are crucially important for the assessment of environmental impact of human activities.

Wednesday, April 27, 2011

Protected area impacts on a global scale

Global protected area impacts

Published online before print November 17, 2010, doi:10.1098/rspb.2010.1713
Proc. R. Soc. B 7 June 2011 vol. 278 no. 17121633-1638

In this paper the researchers estimate the impact of PAs on natural land cover in 147 countries by comparing outcomes inside PAs with outcomes outside. This is an open access paper.


Protected areas play a very important role in conservation scenario. The authors presume that in future they will play a role in future climate policies too, as global payments may reward local reductions of loss of natural land cover.

The researchers use ‘matching’ (or ‘apples to apples’) principle for land characteristics. This is due to the fact that PAs very often are non-randomly distributed across their national landscapes. They say Protection tends towards land that, if unprotected, is less likely than average to be cleared. The research came up with the fact that for 75 per cent of countries protection does reduce conversion of natural land cover. For approximately 80 per cent of countries, the global results also confirm (following smaller-scale studies) that controlling for land characteristics reduces estimated impact by half or more. This researchers’ say shows the importance of controlling for at least a few key land characteristics. They also show that impacts vary considerably within a country (i.e. across a landscape): protection achieves less on lands far from roads, far from cities and on steeper slopes.

The researchers sign off saying that while planners are, of course, constrained by other conservation priorities and costs they could target higher impacts to earn more global payments for reduced deforestation.

Monday, April 25, 2011

Behavioral ecology is fast becoming a threatened discipline says scientists

Endangered species and a threatened discipline: behavioural ecology

Tim Caro and Paul W. Sherman

Trends in Ecology & Evolution, Volume 26, Issue 3, 111-118, 24 January 2011

In this paper the researchers Tim Caro and Paul W. Sherman give vent to their apprehensions that behavioral ecology is fast becoming a threatened discipline in human-dominated landscapes. They say behavioural ecologists often see little connection between the current conservation crisis and the future of their discipline.  They go on to add that this view is myopic because our abilities to investigate and interpret the adaptive significance and evolutionary histories of behaviours are increasingly being compromised in human-dominated landscapes because of species extinctions, habitat destruction, invasive species, pollution, and climate change.

The researchers apprehend that many central issues in behavioural ecology will soon become prohibitively difficult to investigate and interpret, thus impeding the rapid progress that characterizes the field. They advocate that to address these challenges, behavioural ecologists should design studies not only to answer basic scientific questions but also to provide ancillary information for protection and management of their study organisms and habitats, and then share their biological insights with the applied conservation community.

On the whole this paper is very thought provoking.

Saturday, April 23, 2011

First empirical evidence to show that rewilding can work

Resurrecting Extinct Interactions with Extant Substitutes
Current Biology, 21 April 2011

In this paper the researchers say intentional introduction of exotic species is a sure shot way  to fulfill key functions in ecosystems following the loss of recently extinct species. This is the first clear cut evidence to substantiate the hypothesis that exotic species can deliver ecosystem functions of extinct species.
The scene of action is Ile aux Aigrettes, a 25-hectare island off the coast of Mauritius. Ebony ( Diospyros egrettarum )in the island is now critically endangered following intensive logging for firewood. Even though logging was stopped thirty years ago regeneration was far from satisfactory and was taking a nosedive. With the extinction of the island's native giant tortoises, there were no large fruit-eating animals left to disperse the seeds of these critically-endangered trees.
Giant Aldabra tortoises,(Aldabrachelys gigantea) were introduced to reverse the process. The introduced Aldabra tortoises ingested the large fruits and dispersed the ebony seeds. The process of passing through a tortoise's gut gave a further fillip to seed germination. Establishment of new ebony seedlings in the heavily logged parts of the island came in rapidly.
The authors signs off saying “There is increasing evidence that restoration ecologists should be most concerned with the decline of species interactions, rather than species extinctions per se.”

Friday, April 22, 2011

Population variables – A rapid assessment system

A Rapid Method to Estimate Population Variables for African Elephantsno access
Sam M. Ferreira and Rudi J. van Aarde
Journal of Wildlife Management April 2008: Vol. 72, Issue 3, pg(s) 822-829

 Estimation of reproductive and survival parameters for free-ranging animals is of paramount importance. I came across this paper while looking for a rapid assessment method for population variables. The method has the advantage that it is non invasive. The technique was developed by the researchers for free-ranging African savannah elephants (Loxodonta africana africana) based on data at Addo Elephant National Park and Amboseli National Park.

The researchers used published data from 2 populations with known growth rates and birth and survival histories to validate their technique. The technique yielded estimates of age at first and last calving, calving interval, and age-specific survival rates that were similar to those determined during long-term studies at both Addo Elephant National Park and Amboseli National Park. The technique generated population data required to estimate population growth rates.

The researchers conclude that their method may be particularly useful where censuses yield imprecise estimates or where long-term population data are unavailable.

Thursday, April 21, 2011

Biological arms race between the cuckoo finch and its host

I was really fascinated to read about the biological arms races between cuckoos and host birds in Africa. The researchers from University of Cambridge say these sometimes take the form of host evolving new, unique egg patterns (or 'signatures') and the parasite evolving new forgeries.
Here is one strategy. Host females lay a different type of egg, with variations in egg colour and pattern. This makes it harder for the cuckoo finch to come out with accurate forgeries. The researchers say these variations seem to act like the complicated markings on a banknote: complex colours and patterns act to make host eggs more difficult to forge by the parasite, just as watermarks act to make banknotes more difficult to forge by counterfeiters.
The researchers say some host species, such as the tawny-flanked prinia, have evolved defences by shifting their own egg appearance away from that of their parasite. The evidence of this can be seen in the evolution of an amazing diversity of prinia egg colours and patterns.
Red-faced cisticolas lay only moderately variable eggs but are very adept in discerning whether an egg is their own or not. They can easily spot even a sophisticated mimic.
The paper makes interesting reading. It gives us a fascinating insider view of evolution and adaptation
The findings are reported in the journal Proceedings of the Royal Society of B.

 ‘How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences’
Claire N. Spottiswoode and Martin Stevens

Wednesday, April 20, 2011

Wildlife management – A game-theoretic approach

In this paper the authors contend that management strategies provided by the game-theoretic approach complements existing adaptive management methodologies.
Conservation problems usually involve groups with competing objectives and strategies. In this scenario   Identifying dependencies between competing strategies and determining which action optimally achieves the appropriate conservation goals  is of paramount importance for effective evolution of appropriate strategies.
The authors show how several real-world conservation problems can be modeled game-theoretically. The analysis is based on multi-national conservation cooperation, management of common-pool resources, and games against nature. 
The researchers contend that game-theoretic models suggest potential solutions that are often invisible to the usual management protocol: decision followed by monitoring, feedback and revised decisions. 

Mark Colyvan, James Justus, Helen M. Regan
Pages 1246-1253, Volume 144, Issue 4(April 2011) , Adaptive management for biodiversity conservation in an uncertain world
Edited by David A. Keith, Tara G. Martin and Eve McDonald-Madden,  Biological Conservation

Thursday, April 14, 2011

No update for one week

Hi Guys,
              I am travelling to areas with no internet connectivity for the next seven days. Consequently there won't be any updates during this period.

Wednesday, April 13, 2011

Putting Allee effects to good use

Exploiting Allee effects for managing biological invasions
Patrick C. Tobin, Luděk Berec, Andrew M. Liebhold
Article first published online: 22 MAR 2011
Ecology Letters 

Putting Allee effects to good use? Sounds a wee bit far fetched.Yes, this is exactly what is discussed in this paper.
Biological invasions are an increasing threat to biodiversity worldwide. Allee effects (positive density dependence) have been shown to play a pivotal role in the spread of exotic species (non-native species).  Allee effects are a nuisance in conservation efforts, but they can prove useful in attempts to manage non-native species.
In this paper the authors review and highlight current strategies that effectively exploit an Allee effect. They propose ingenious ways by which Allee effects can be manipulated to the detriment of biological invaders. They contend that the concept of Allee effects can be integral in risk assessments and in the prioritization of resources allocated to manage non-native species, as some species beset by strong Allee effects could be less successful as invaders. The authors describe how methodologies that strengthen an existing Allee effect or create new ones could be used to manage biological invasions more effectively. On the whole a very interesting paper

Tuesday, April 12, 2011

Predator-driven component Allee effects may exacerbate the risk of extinction of small populations

Predator-driven component Allee effects in a wild ungulate
Aurélie Bourbeau-Lemieux, Marco Festa-Bianchet,Jean-Michel Gaillard,Fanie Pelletier
Article first published online: 15 FEB 2011
Ecology Letters
DOI: 10.1111/j.1461-0248.2011.01595.x
Here is a good paper on exacerbating effects of Allee effects (positive density dependence) on small populations. Negative density dependence of course is an important driver of population dynamics of large vertebrates. 
Allee effects can be generated by predation. Recent research has come up with potentially important indirect effects of predation on population dynamics. The researchers monitored for 27 years a bighorn sheep (Ovis canadensis) population that declined dramatically as cougar (Puma concolor) predation depressed survival. The researchers say predation led to a positive relationship between lamb survival and population size below a threshold, and to an overall positive relationship between yearling and adult ewe survival and population size. 
During years of high predation, lambs also suffer mortality through reduced growth. This contributed to a third of the total impact of predation on lamb survival. 
The researchers sign off saying “Our results support the contention that predator-driven component Allee effects may exacerbate the effects of other environmental drivers and increase the risk of extinction of small populations”.

Monday, April 11, 2011

A new look at predator prey relationships

A new paper by University of Notre Dame biologist Gary Belovsky appearing in the latest issue of journal Ecology Letters drives home the point that predator-prey relationships are much more complex than originally thought.
Belovsky studied   how behavioral responses of grasshoppers to avian predators affected grasshopper survival and reproduction at different grasshopper population densities. He arranged a series of cages containing grasshoppers. These cages were enclosed within a tent constructed of aviary netting. He designated it as a "no threat" area because its design prevented birds from approaching the cages and "scaring" the grasshoppers. A second set of cages were provided that were not enclosed in tent. Belvosky designated it as a "threat" area .This allowed birds to feed around the cages, perch on top consuming grasshoppers caught outside the cages and "scare" the grasshoppers inside the cages.

The research demonstrated that grasshopper behavior changed with the threat of predators. The behavioral changes with the threat of predation increased survival at low grasshopper densities. Reduced feeding made food available to more individuals. While the changes decreased survival at higher densities, food shortages were made worse by reduced feeding. The behavioral changes decreased per capita reproduction over all grasshopper population densities.  Behavioral changes increased survival at low grasshopper densities and then decreased survival at high densities. At low grasshopper densities, the total reproductive output of the grasshopper population remained unchanged with predation threat, but declined at higher densities.
Usually this type of variable response is overlooked when prey predation relationships are considered. The researcher says resource availability may need to be considered when assessing how prey behavior changes with predation and how the threats affect population and food web dynamics.
Prey change behaviour with predation threat, but demographic effects varies with prey density: Experiments with grasshoppers and birds
Gary E. Belovsky, Angela Nardoni Laws. Jennifer B. Slade
Ecology Letters (2011) 14: 335–340

Sunday, April 10, 2011

A new index to assess mammal species that are most likely to become extinct

A new index called   SAFE (Species Ability to Forestall Extinction) has been developed by a team of Australian researchers from the University of Adelaide and James Cook University. This will help conservationists better understand how close species are to extinction.

The SAFE index is an improvement on previous studies into the minimum population sizes needed by species to survive in the wild. It gives a measure of how close species are to their minimum viable population size. It is an assessment of the distance a population is (in terms of abundance) from its minimum viable population size
According to the researchers SAFE is the best predictor yet of the vulnerability of mammal species to extinction. It is not intended to replace IUCN threat categorization but the SAFE index provides a more meaningful and fine-grained interpretation of the relative threat of species extinction than do the IUCN threat categories alone.
The team analyzed 95 mammals species and found nearly 60% are close to a 'tipping point' that could push the species to extinction. 25% are already close to extinction. The researchers aver that their analyses allow conservationists a better tool to determine where to spend funds and time. 

The SAFE index: using a threshold population target to measure relative species threat.    Gopalasamy Reuben Clements, Corey JA Bradshaw, Barry W Brook and William F Laurance.  Frontiers in Ecology and the Environment.

Saturday, April 09, 2011

Mangrove forests and carbon sequestration

According to a new study published on April 3, in Nature Geoscience, mangroves store exceptionally more carbon than most tropical forests. The flip side is that Mangroves are being destroyed at an alarming rate. Mangrove forests have declined by as much as 50% over the past half century.
According to the researchers even though mangroves occupy less than 1% of tropical forest area, they store up to 10% of global carbon emissions. Till now the amount of carbon in mangroves has been largely ignored.
To estimate the abundance of carbon in mangroves, lead investigator J. Boone Kauffman, an ecologist at the Northern Research Station of the US Forest Service in Durham, New Hampshire, and his team sampled 25 mangrove sites across the world that covered about 40% of the global area covered by these forests. They found that these forests hold much more carbon than boreal, temperate or tropical upland forests. The carbon was stored mainly in an organic-rich 'muck layer' of soil more than 30 centimeters below the surface. The researchers assess that worldwide carbon reserves in mangrove forests may be as high as 25% of those in tropical peatlands. The researchers sound the warning that destroying mangrove forests could have far reaching deleterious effects.
The paper gives a germane justification for preserving mangrove forests. It is also a wakeup call.

Mangroves among the most carbon-rich forests in the tropics

Nature Geoscience (2011) doi: 10.1038/ngeo1123

Friday, April 08, 2011

An assessment of the reliability of ground counts of ungulate populations

 Ground counts are often used to monitor ungulate populations. The minus point is that ground counts have low precision and often underestimate population size.

The authors of this paper assessed the reliability of ibex Capra ibex counts as performed in French national parks. They analysed up to 23 years of annual censuses of six ibex populations. The population growth rate obtained from census data (estimated by use of four different methods) was compared with the growth rate calculated from a demographic model including parameters estimated from capture-mark-recapture methods.

The results suggested that ground counts can monitor trends in population size of ibex, provided the occasional undercounts are identified. The authors say substantial undercounts in some years led to biologically impossible values of yearly population growth (λ > 1.35) and, in the longest time series available, to marked autocorrelations in counts.

The researchers come up with the recommendation that managers should replicate counts within the same year to check for underestimated counts. To reduce errors, population biologists analyzing time series of ungulate counts should check the plausibility of annual growth rates estimated from two consecutive counts.

Can ground counts reliably monitor ibex Capra ibexpopulations?
Emilie Largo, Jean-Michel Gaillard, Marco Festa-Bianchet, Carole Toïgo, Bruno Bassano, Hervé Cortot, Gilles Farny, Benoît Lequette, Dominique Gauthier & Jean-Pierre Martinot
Wildl. Biol. 14: 489-499.

Wednesday, April 06, 2011

Habitat fragmentation, percolation theory and the conservation of a keystone species

Habitat fragmentation, percolation theory and the conservation of a keystone species
Proceedings: Biological Sciences © 1998. The Royal Society

This paper is worth a read. The authors say sustainable forest–harvesting strategies may not be as successful as is currently thought. They also impute that habitat corridors, once thought of as the saviour for fragmented environments, may have a detrimental effect on population in certain cases.

Many species survive in specialized habitats. When these habitats are destroyed or fragmented the threat of extinction looms large. In this paper, the authors use percolation theory to consider how an environment may fragment. They then developed a stochastic, spatially explicit, individual-based model to consider the effect of habitat fragmentation on a keystone species (the army ant Eciton burchelli) in a neo tropical rainforest. The results point to the fact that that species may become extinct even in huge reserves before their habitat is fully fragmented. This aspect of the results of the study has important implications for conservation

The authors discuss the appropriateness of corridors.  They say for species that possess no `long-term memory’ corridors between reserves have to be sufficiently large so that the corridors can be found, and second they can be negotiated successfully. It is hard to lay down any minimum corridor size, since divergently shaped lattices and different models for local movements will yield different answers. The researchers say that there is a minimum corridor width between small reserves to ensure the persistence of a population. They observed persistence to be impossible if pockets of habitat are hard to find. Geometrically complicated reserves are of little use to the keystone species Eciton burchelli . A colony become strapped in a small pocket of rainforest, depleting its local resources and thus faces starvation. It could be possible for this situation to be repeated in a habitat corridor and an individual (with poor or no navigational skills) enters a corridor, wanders back and forth, depleting its resources, and therefore leading to starvation. A corridor that would suit one species might be detrimental to others.

On the whole this paper is very thought provoking.

Tuesday, April 05, 2011

Planning, implementing, and monitoring multiple-species habitat conservation plans

Planning, implementing, and monitoring multiple-species habitat conservation plans
Janet Franklin, Helen M. Regan, Lauren A. Hierl, Douglas H. Deutschman, Brenda S. Johnson and Clark S. Winchell
First published online February 25, 2011; doi:10.3732/ajb.1000292
American Journal of Botany 98: 559-571 (2011)

Here is a good paper on planning, implementing, and monitoring multiple-species habitat conservation plans.
Systematic conservation planning is sine qua non in conservation biology both in academic circles and on-the-ground conservation initiatives. Nature reserves comprise geographical areas of the land or sea, managed for conservation, where protection of designated species or other ecosystem holds sway. Certain human activities are limited or prohibited.

The authors say once a nature reserve or conservation plan has been designed and established, the work is just beginning. Ongoing monitoring is required of institutional entities responsible for managing reserves, because monitoring is critical for determining whether conservation plans are meeting their goals. Sadly monitoring programs to assess the efficacy of conservation plans to meet their stated objectives are often lacking. Often monitoring activities occur in an ad hoc and piecemeal fashion.

This paper reviews major themes in biodiversity conservation planning and then focuses on monitoring. Recent developments in, and recommendations for, monitoring design for conservation plans are explicitly discussed.