The significance of visual ‘nectar guides’

Floral signposts: testing the significance of visual ‘nectar guides’ for pollinator behaviour and plant fitness

Dennis M. Hansen,Timotheüs Van der Niet and Steven D. Johnson

Published online before print July 27, 2011, doi:10.1098/rspb.2011.1349Proc. R. Soc. B

Yesterday we were  discussing about the leaves that act like neon signs in restaurants. Here is another feature that is akin to what we were discussing. This time it is nectar guides, contrasting patterns on flowers that direct pollinators towards a concealed nectar reward.

The researchers experimentally investigated the role of nectar guides in a natural system, the South African iris Lapeirousia oreogena, whose flowers have a clearly visible pattern of six white arrow markings pointing towards the narrow entrance of the long corolla tube. The sole pollinator is a long-proboscid nemestrinid fly.

The investigators painted over none, some or all of the white arrow-markings with ink that matched the colour of the corolla background. Aarrow-marking removal had little effect on the approaches by flies to flowers from a distance, but it significantly, and according to the words of the researchers dramatically reduced the likelihood of proboscis insertion. The researchers say export of pollen dye analogue (an estimate of male fitness) was reduced to almost zero in flowers from which all nectar guides had been removed, and fruit set (a measure of female fitness) was also significantly reduced. 

According to the researchers their experiments confirm that the markings on L. oreogena flowers serve as nectar guides and suggest that they are under strong selective maintenance through both male and female fitness components in this pollination system.

Leaves that act like neon signs in restaurants

Floral Acoustics: Conspicuous Echoes of a Dish-Shaped Leaf Attract Bat Pollinators

Ralph Simon,Marc W. Holderied,Corinna U. Koch,Otto von Helversen

Science 29 July 2011: 
Vol. 333 no. 6042 pp. 631-633 
DOI: 10.1126/science.1204210

Restaurants usually have eye catching neon signs to attract customers. Researchers have come up with an analogy from the natural word. Scientists have just described the behavior of a vine (Marcgravia evenia ) found in Cuban jungle, that puts forth unusual dish-shaped leaf displayed above the inflorescences to attract bats.

The special leaf makes the wine more conspicuous to the sonar of bats and acts like a dish reflector. This leaf’s echoes fulfilled requirements for an effective beacon.  They were strong and multidirectional

According to the researchers this is an interesting example of the ongoing coevolution of flowering plants and their animal pollinators,

All is not well with protected area networks says researchers

Ongoing global biodiversity loss and the need to move beyond protected areas: a review of the technical and practical shortcomings of protected areas on land and sea

Camilo Mora and Peter F. Sale

MARINE ECOLOGY PROGRESS SERIES

Mar Ecol Prog Ser

Vol. 434: 251–266, 2011

doi: 10.3354/meps09214

Here is a thought provoking paper on, protected areas and its effectiveness. The researchers relied on a broad range of data and a review of the literature to show that the effectiveness of existing, and the current pace of the establishment of new, protected areas will not be able to overcome current trends of loss of marine and terrestrial biodiversity.

The authors say there are significant shortcomings in the usual process of implementation of protected areas. They go on to add that the shortcomings include techni-cal problems associated with large gaps in the coverage of critical ecological processes related to individual home ranges and propagule dispersal, and the overall failure of such areas to protect against the broad range of threats affecting ecosystems. They stress the point that budget constraints, conflicts with human development, and a growing human population that will increase not only the extent of anthropogenic stressors but the difficulty in successfully enforcing protected areas.

The authors sign off with these words  “Whileefforts towards improving and increasing the number and/or size of protected areas must continue, there is a clear and urgent need for the development of additional solutions for biodiversity loss, particularly ones that stabilize the size of the world’s human population and our ecological demands on biodiversity”

The first "true mammal" to sense prey by their electric fields

Electroreception in the Guiana dolphin (Sotalia guianensis)

Nicole U. Czech-Damal, Alexander Liebschner,Lars Miersch,Gertrud Klauer,Frederike D. Hanke,Christopher Marshall,Guido Dehnhardt,and Wolf Hanke

Published online before print July 27, 2011, doi:10.1098/rspb.2011.1127 Proc. R. Soc. B

The South American  Guiana dolphin (Sotalia guianensis) has just been described as the only  "true mammal" to sense prey by their electric fields. Even though Electroreception is well known in fish and amphibians, till now the only mammal example was the platypus.

In the paper referred to above the scientists  show that the hairless vibrissal crypts on the rostrum of the Guiana dolphin, structures originally associated with the mammalian whiskers, serve as electroreceptors in Guiana dolphin.

The researchers recorded a sensory detection threshold for weak electric fields of 4.6 µV cm⁻¹, which is comparable to the sensitivity of electroreceptors in platypuses.

Now the researchers plan to investigate whether other cetaceans possess the same ability.

Spatially balanced acoustic surveys for bats

A practical sampling design for acoustic surveys of bats

Thomas J. Rodhouse, Kerri T. Vierling, Kathryn M. Irvine

Wildlife Management - Article first published online: 21 APR 2011

Acoustic surveys are regularly put to use to find out bat occurrence and activity patterns. It comes in very handy for addressing concerns for habitat management, wind energy, and disease on bat populations. 

When a probabilistic sample is required for drawing inference to unsampled areas,  devising these surveys becomes a wee bit difficult. Sampling frame errors and other logistical constraints often makes it essential for survey sites to be dropped from the sample and new sites added. Here crops up difficulties.

The authors of this paper say spatially balanced sampling designs recently developed to support aquatic surveys along rivers provide solutions to a number of practical challenges faced by bat researchers. These techniques allow sample site additions and deletions, support unequal-probability selection of sites, and provide an approximately unbiased local neighborhood-weighted variance estimator that is efficient for spatially structured populations such as bats.

Taking cue from the above mentioned technique the researchers implemented a spatially balanced design to survey canyon bat (Parastrellus hesperus) activity along a stream network. This provided leeway for typical logistical challenges and yielded a 25% smaller estimated standard error for the mean activity level than the usual simple random sampling estimator.

The authors signs off like this  “Spatially balanced designs have broad application to bat research and monitoring programs and will improve studies relying on model-based inference (e.g., occupancy models) by providing flexibility and protection against violations of the independence assumption, even if design-based estimators are not used. Our approach is scalable and can be used for pre- and post-construction surveys along wind turbine arrays and for regional monitoring programs.”

Book Recommendation

Trophic Cascades

Predators, Prey, and the Changing Dynamics of Nature

John Terborgh, James Estes

Publisher: Island Press
456 p. 7"x10"
ISBN: 9781597264877

Here is a very good book on Trophic cascads, the top-down regulation of ecosystems by predators. Trophic cascades are often turned topsy-turvy by human interventions. The book bucks the idea of "bottom up" regulation of ecosystems. It graphically describes the consequences of apex predator elimination which results in a chain reaction, or "cascade" of effects down to the lowest level of the trophic ladder.

In recent years Trophic cascads have started assuming increasing influence in the development of conservation and management strategies.

Marco Polo Sheep is an international traveller

An analysis of DNA from fecal samples by researchers from WCS has come up with the finding that Marco Polo sheep in the Pamir Mountains of Afghanistan are genetically connected to sheep in neighboring Tajikistan and China, despite the difficult terrain.

The researchers involved are Dr Richard.B. Harris of the University of Montana, Dr John Winnie, Jr.of Montana State University, Dr Gordon Luikart, Stephen, Dr J. Amish, and Dr F.W. Allendorf of the University of Montana, and Dr Albano Beja-Pereira, Vânia Costa, and Dr Raquel Godinho of the Universidade do Porto

The research team collected fecal samples from 172 individual sheep from five different areas in Afghanistan, Tajikistan to arrive at their conclusions.

The research highlighted the fact that non-invasive methods of determining population trends and relatedness are extremely valuable in devising conservation strategy for animals that are elusive and difficult to track. It also highlighted the need for international cooperation between Afghanistan, Tajikistan, and China.

Long-term preventive conservation is preferable to short term firefighting

When should we save the most endangered species?

Howard B. Wilson,Liana N Joseph,Alana L. Moore and Hugh P. Possingham

Article first published online: 12 JUL 2011

Ecology Letters (2011)

In this paper the authors emphasizes that long-term preventive conservation measures are far better than short term firefighting

Conservationists have always been bothered whether to give priority to cost-effective actions or whether focusing solely on the most endangered species will ultimately lead to preservation of the greatest number of species. Conservation funding tends to be short-term in nature and on the whole biased to more endangered species.

By framing this debate within a decision-analytic framework, the researchers show that allocating resources solely to the most endangered species will typically not minimise the number of extinctions in the long-term, as this does not account for the risk of less endangered species going extinct in the future.

Short term fire fighting can be resorted to when our planning timeframe is short or we have a long-term view and we are optimistic about future conditions.

On the whole this paper is very thought provoking.

Connectivity, patch based graphs, and conservation

Patch-based graphs of landscape connectivity: A guide to construction, analysis and application for conservation

Paul Galpern Micheline Manseau and Andrew Fall

Biological Conservation
Volume 144, Issue 1, January 2011, Pages 44-55

Here is a good paper that deals with connectivity and the use of patch based graphs.

Connectivity is a major conservation priority. Maintaining connectivity and mitigating the fragmentation of habitat is critical for landscape processes. For modelling the functional connectivity of landscapes, Graph theory (also known as network analysis), has become sine qua non for many researchers and managers.  The authors of this paper say they conducted a review of studies that use graph theory to model connectivity among patches of habitat (patch-based graphs), with the intention of identifying typical research questions and their associated graph construction and analysis methods.

The researchers identified and examined nine questions of conservation importance that can be answered with these types of graph models. They discussed appropriate applications of these questions and presented a guide for using graph methods to answer them. They also examined how the connectivity predictions of patch-based graphs have been assessed and emphasize the importance of empirical evaluation.

The researchers sign off like this “. Our findings identify commonality among diverse approaches and methodological gaps with an aim to improve application and to help the integration of graph theory and ecological analysis.”  “As a final caveat, we urge those using patch-based graphs in a decision-making process to assess the relative importance of conserving connectivity compared to, for example, conservation decisions based only on the amount and quality of habitat. This remains an important area for further theoretical and empirical consideration”

Snap-buckling observed in vertebrates for the first time

Snap-buckling is usually seen in plants and insects. It is akin to the opening and closing of a snap hair clip

 The best example of snap-buckling in plants is the Venus flytrap, which uses it to catch insects.

For the first time Snap-buckling has been observed in vertebrates and it happens to be in hummingbird.

Hummingbird beaks are built to feed on flowers, but hummingbirds can't live on nectar alone. To get enough protein and nutrients they need to eat small insects also. The shape of a hummingbird's beak allows for “controlled elastic" and this allows it to snatch up flying insects in a mere fraction of seconds.

The researchers found that the hummingbird's bendy lower beak flexes by as much as 25 degrees when it opens. At the same time it also widens at the base to create a larger surface for catching insects. The extra speed leads to greater success in catching insects.

Details of the study will appear in the August 7 issue of Journal of Theoretical Biology

Conservation success story - Grand Cayman blue iguana is back from the brink of extinction

         Credit: Julie Larsen Maher/Wildlife Conservation Society.

We constantly hear about species on the brink of extinction. In many cases efforts to save them seem a distant possibility. Here is a rarity in conservation, a conservation effort that bucks the trend.

Blue Iguana Recovery Program in Cayman Island is well on its way to success. Blue iguana is the largest native species of Cayman Island. Coordinated by the National Trust for the Cayman Islands, the Blue Iguana Recovery Program—a consortium of local and international partners—has successfully released more than 500 captive-bred reptiles since the initiative's inception in 2002. In 2002 wild population of iguanas numbered less than two dozen. Conservationists expect to reach their goal of 1,000 iguanas in managed protected areas in the wild in a few years.


Recovery efforts to save the Grand Cayman blue iguana have mostly centered on the Salina Reserve, a 625-acre nature reserve located on the eastern side of the island. This year the efforts move on to newly established Colliers Wilderness Reserve also.

The importance of survey design in distance sampling

The importance of survey design in distance sampling: field evaluation using domestic sheep
Tom A. Porteus, Suzanne M. Richardson, and Jonathan C. Reynolds

Wildlife Research 38(3) 221-234 http://dx.doi.org/10.1071/WR10234

Wildlife managers and researchers regularly use distance sampling. Here is a paper that emphasizes the importance of survey design in distance sample. Management decisions are often made based on these estimates. Without knowledge of true population size it is not possible for wildlife biologists to evaluate how biased the estimates can be if survey design is compromised.

Here the researchers did a clever field evaluation using domestic sheep. Their aims were to use distance sampling to estimate population size for domestic sheep free-ranging within large enclosed areas of hill country. By comparing estimates against actual numbers, they examined how bias and precision are impaired when survey design is compromised

Both line and point transect sampling were used to derive estimates of density for sheep on four farms in upland England. In Stage I they used limited effort and different transect types to compromise survey design. In Stage II they increased effort in an attempt to improve on the Stage I estimates. They also examined the influence of a walking observer on sheep behaviour to assess compliance with distance sampling assumptions and to improve the fit of models to the data.

The results clearly demonstrated that distance sampling can lead to biased and imprecise density estimates if survey design is poor, particularly when sampling high density and mobile species that respond to observer presence. The researchers say in Stage I, walked line transects were least biased; point transects were most biased. Increased effort in Stage II reduced the bias in walked line transect estimates. For all estimates, the actual density was within the derived 95% confidence intervals, but some of these spanned a range of over 100 sheep per km².

The researchers have clearly shown that survey design is vitally important in achieving unbiased and precise density estimation using distance sampling. Adequate transect replication reduced the bias considerably within a compromised survey design.

The researchers sign off like this “Management decisions based on poorly designed surveys must be made with an appropriate understanding of estimate uncertainty. Failure to do this may lead to ineffective management.”

Tailpiece: We had sent mail to one wildlife warden regarding the poor design of some of his census techniques. We had also requested him to contact well versed scientists to set things right. He never responded. This post is intended to show him and his ilk how design flaws can throw the entire process out of kilter.

Sexual segregation in Giant Pandas

Different habitat preferences of male and female giant pandas

Dunwu Qi,Shanning Zhang,Zejun Zhang,Yibo Hu,Xuyu Yang,Hongjia Wang,Fuwen Wei

Article first published online: 5 JUL 2011 Journal of Zoology

DOI: 10.1111/j.1469-7998.2011.00831.x

Now here is a surprise. According to this study male and female giant pandas prefer to use different habitats. Using a combination of field surveys and sex identification through fecal DNA, the researchers investigated gender differences in habitat use in wild giant pandas through ecological niche factor analysis modelling. 

Female pandas frequent high altitude conifer forests and mixed forests on steeper slopes, whereas males roam about more widely, researchers discovered. Females stuck to these areas as they provide den sites for birthing and dense bamboo cover in which baby pandas can hide.

The researchers say these findings should be taken into account when breeding programmes for release of giant pandas back into the wild are devised.

First insights into Sumatran tiger–prey temporal interactions

Assessing tiger–prey interactions in Sumatran rainforests

M. Linkie AND M. S. Ridout

Journal of Zoology

Volume 284, Issue 3, pages 224–229, July 2011

Very little is known about Sumatran tiger–prey temporal interactions. Here the researchers are trying to unravel the mystery surrounding   Sumatran tiger ( Panthera tigris Sumatra)

The researchers quantify temporal overlap between the Sumatran tiger and five of its presumed prey species. This was from four study areas comprising disturbed lowland to primary submontane forest data from 126 camera traps.  Over 8984 camera days were used to estimate species activity patterns and, the overlap through the coefficient Δ (ranging from 0 to 1, i.e. no overlap to complete overlap). 

To determine confidence intervals associated with respective overlap a newly developed statistical technique was used.

Strong temporal overlap was found between tiger and muntjac Muntiacus muntjac (Δ=0.80, 95%CI=0.71–0.84) and tiger and sambarCervus unicolor (Δ=0.81, 0.55–0.85).

The authors signs off like this “ According to the foraging theory, Sumatran tigers should focus on expending lower levels of energy searching for and then capturing larger bodied prey that present the least risk. Hence, surprisingly, there was little overlap between the crepuscular tiger and the largest-bodied prey species available, the nocturnal tapir Tapirus indicus (0.52, 0.44–0.60), suggesting that it is not a principal prey species. This study provides the first insights into Sumatran tiger–prey temporal interactions. The ability to estimate overlap statistics with measures of precision has obvious and wide benefits for other predator–prey and interspecific competition studies.”

Do solitary foraging nocturnal small mammals plan their routes?

Do solitary foraging nocturnal mammals plan their routes?

Marine Joly and Elke Zimmermann

Published online before print April 27, 2011, doi:10.1098/rsbl.2011.0258Biol. Lett. 23 August 2011 vol. 7 no. 4 638-640

Here is a thought provoking paper on small mammals.

It is an established fact that large-brained diurnal mammals with complex social systems plan where and how to reach a resource. This is established by a systematic movement pattern analysis.

Here the researchers examined for the first time large-scale movement patterns of a solitary-ranging and small-brained mammal, the mouse lemur (Microcebus murinus). They used the change-point test and a heuristic random travel model to get insight into foraging strategies and route-planning abilities.

Seven lemurs were radio-collared and their foraging patterns examined. The researchers say the change-points coincided with out-of-sight keystone food resources. Travel paths were more efficient in detecting these resources than a heuristic random travel model within limits of estimated detection distance.

The researchers signs off suggesting that even nocturnal, solitary-ranging mammals with small brains plan their route to an out-of-sight target. Thus, similar ecological pressures may lead to comparable spatial cognitive skills irrespective of the degree of sociality or relative brain size.

Circumventing limitations of GIS technology

Greater Sage-Grouse Nesting Habitat: The Importance of Managing at Multiple Scales

Doherty, K.E., Naugle, D.E. & Walker, B.L. Greater Sage-Grouse Nesting Habitat: The Importance of Managing at Multiple Scales. Journal of Wildlife Management 74, 1544-1553 (2010).

The other day I was discussing with my friend Ramesh, the limitations of use of GIS in wildlife management.  GIS often takes in to account only landscape scale vegetation patterns. This is the result of extreme resolution required to know about local level vegetation characteristics from satellite imagery.  The starting point was a 2010 paper referred to above. Here is a paper that looks at the limitations of GIS. The researchers come up with alternate solutions to plug the loop.

A close look at habitat selection at multiple scales is essential to fully understand habitat requirements and dovetail it to the management needs for wildlife. The researchers used a hierarchical information-theoretic approach and variance decomposition techniques to analyze habitat selection using local-scale habitat variables measured in the field and landscape-scale variables derived with a Geographic Information System (GIS) for nesting greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB), Montana and Wyoming, USA.

The authors say variance decomposition showed that local-scale measures explained the most pure variation (50%) in sage-grouse nesting-habitat selection. Landscape-scale features explained 20% of pure variation and shared 30% with local-scale features. The landscape-scale model produced was accurate in predicting priority landscapes where sage-grouse nests would occur and is, therefore, useful in providing landscape context for management decisions. It accurately predicted locations of independent sage-grouse nests (validation R²  =  0.99) and showed good discriminatory ability with >90% of nests located within only 40% of the study area.

The model also accurately predicted independent lek locations and supported predictions of the hotspot theory of lek placement. 

The authors signs off saying “ Local-scale habitat variables that cannot currently be mapped in a GIS strongly influence sage-grouse nest-site selection, but only within priority nesting habitats defined at the landscape scale. Our results indicate that habitat treatments for nesting sage-grouse applied in areas with an unsuitable landscape context are unlikely to achieve desired conservation results.”

Understanding the effect of human-driven changes on population performance of long-lived species

Decomposing variation in population growth into contributions from environment and phenotypes in an age-structured population

Fanie Pelletier,Kelly Moyes,Tim H. Clutton-Brock andTim Coulson

Published online before print June 29, 2011, doi:10.1098/rspb.2011.0827 Proc. R. Soc. B

Here is a new paper that attempts to understand the effect of human-driven changes on population performance of long-lived species. It is not an easy task. It is a real challenge to come to grips with the relative importance of ecological drivers responsible for natural population fluctuations.

The authors used a recently developed approach to decompose the observed fluctuation in population growth of the red deer population on the Isle of Rum into contributions from climate, density and their interaction and to quantify their relative importance. They also quantified the contribution of individual covariates, including phenotypic and life-history traits, to population growth.

Fluctuations in composition in age and sex classes of the population contributed substantially to the population dynamics. Density, climate, birth weight and reproductive status contributed less and approximately equally to the population growth.

The researchers signs off saying “ Our results support the contention that fluctuations in the population's structure have important consequences for population dynamics and underline the importance of including information on population composition to understand the effect of human-driven changes on population performance of long-lived species.

Light at the end of the tunnel for Dr Ullas Karanth

We all are aware of the trials and tribulations that Dr Ullas Karanth had to undergo while doing his research on tigers in Karnataka. He was hassled unnecessarily. Profesional jealousy added salt to the wound. But things have suddenly started looking very rosy for the renowned scientist.

Centre for Wildlife Studies headed by Dr Ullas Karanth  has been recognized as a "Centre of Excellence" by the Government of Karnataka for its contribution to conservation biology over the pas two decades. The ongoing project titled "Meta-Population dynamics of tigers in Malenad-Mysore Tiger Landscape (MMTL) of Karnataka" conducted in collaboration with the Karnataka Forest Department has come in for laurels.The Award was presented to  Dr. Ullas Karanth, by Chief Minister of Karnataka B. S. Yeddyurappa at a function held in Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore on 6th July 2011. 

My views on this mirrors what Dr. George Schaller said. In a congratulatory message to Dr Ullas Karanth he  said " It is so well deserved, and it's wonderful to  see that after years of getting hassled or your important work ignored you are finally recognized officially and valued”.

We wish Dr Ullas Karanth many more years of fruitful, research. You have shown the youngsters what grit can do.