Archive for July, 2007

Jul

31

2007
 
 

Dog days for evidence



Knowing what went right and what went wrong are key to better practice

packWhen you’ve got a self-sustaining, minimally managed population, your reintroduction project has been a success. Sadly, most fail, yet we haven’t learned much from our mistakes. What we need, according to a study published recently in the Journal of Applied Ecology, is a methodology based on evidence and not belief. To illustrate what they mean, the University of KwaZulu-Natal’s Markus Gusset, the University of California, Berkeley’s Sadie Ryan and a pack of colleagues analysed the intensive efforts to restore populations of wild dogs Lycaon pictus to an increasingly fragmented South African landscape. Looking at a wide range of factors that might affect the survival of introduced dogs and their ability to produce pups, the researchers found just two of major importance. The length of time dogs spend social bonding in a boma — their cohesiveness is crucial to survival — and the boundary security of the area into which they are released should be foremost among management decisions. Minimal management might be some way off, but in the meantime at least we can concentrate on what’s important. Source: Gusset M, Ryan SJ, Hofmeyr M, Van Dyk G, Davies-Mostert HT, Graf JA, Owen C, Szykman M, Macdonald DW, Monfort SL, Wildt DE, Maddock AH, Mills MGL, Slotow R & Somers MJ (2007) Efforts going to the dogs? Evaluating attempts to re-introduce endangered wild dogs in South Africa. Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2007.01357.x

Related story in Conservation magazine: Where the Wild Things Were

Image © Peter Malsbury

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Jul

26

2007
 
 

Earthworms steal the floor



Invasion by non-native earthworms triggers decline in plant diversity

nobody loves meIf plants are disappearing all around you, check underneath your wellies — it could be down to invading earthworms. Andrew Holdsworth and University of Minnesota colleagues describe in Conservation Biology how declines in plant diversity in two national forests — Chippewa and Chequamegon — can be traced to the recent arrival of European Lumbricus earthworms. Earthworm invasions are associated with the removal of the forest floor, which in turn leads to a reduction in plant species richness. Such a link has been suspected for some time, but difficult to disentangle from other factors, such as browsing pressure from white-tailed deer Odocoileus virginianus. Holdsworth’s analysis reveals the scope of the impact worms have. The good news is that the wriggly ecosystem engineers aren’t exactly the fastest colonizers around, so education and vigilance should help identify and protect those areas most under threat. Source: Holdsworth AR, Frelich LE & Reich PB (2007) Effects of earthworm invasion on plant species richness in Northern hardwood forests. Conservation Biology DOI: 10.1111/j.1523-1739.2007.00740.x

Related stories in Conservation magazine: Nonnative Earthworms May Be Wiping Out Rare Plants | Can Rodents Save The Planet?

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Jul

25

2007
 
 

Love Marmite? You should



Dietary specialization is a one-way ticket to oblivion, bat study finds

picky eaterCosmopolitan tastes are good for one’s survival prospects, according to a study published this week in PLoS ONE. Indiana State University biologists Justin Boyles and Jon Storm analyzed the dietary habits of vespertilionid bat species in relation to their IUCN conservation status. Species of least concern enjoy a wider range of prey than those considered to be near threatened, vulnerable or endangered. Although the findings suggest that dietary specialization on its own is not enough to put a species at risk, they strongly suggest it’s a confounding factor. So eat your sprouts and think on. Source: Boyles JG & Storm JJ (2007) The perils of picky eating: dietary breadth is related to extinction risk in insectivorous bats. PLoS ONE DOI: 10.1371/journal.pone.0000672

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Jul

25

2007
 
 

Can rodents save the planet?



Invasive species can have a dramatic effect on carbon sequestration

rat on a ropeRats profoundly change the amount of carbon stored in island plants, according to a paper published today in Biology Letters. Landcare Research ecologist David Wardle and colleagues measured the amount of carbon stored above and below ground at eighteen forested islands off the New Zealand coast. Burrowing seabirds, whose eggs and chicks form a tasty part of an introduced rat’s diet, damage plant root systems as they dig. This can reduce the growth rate of trees; at the same time, carbon-laden material is brought down from the surface. Rat predation causes drastic reductions in seabird numbers, shifting the pattern of carbon sequestration in favor of aboveground storage within healthier, more vigorously growing plants. All told, a rat invasion increases total ecosystem carbon uptake by 37%. Hands up who saw that one coming! Source: Wardle DA, Bellingham PJ, Fukami T & Mulder CPH (2007) Promotion of ecosystem carbon sequestration by invasive predators. Biology Letters DOI 10.1098/rsbl.2007.0163

Image © Heiko Etzrodt

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Jul

23

2007
 
 

Flying in the face of extinction



Rare butterfly is surprisingly mobile, a trait that could save it from oblivion

another species slipping through the net?Why are some species rare when their close relatives are common? A study of the sister butterfly species Orachrysops ariadne (the rare one) and O. subravus (its common counterpart) might provide the answer, according to University of Stellenbosch entomologist Michael Samways and co-author Shen-Shan Lu. Using mark-recapture techniques they discovered that whilst O. ariadne is indeed staggeringly rare, it’s not down to poor flying skills as one might predict. The findings, published in Biodiversity and Conservation, show that in fact it flies better than the much more widespread O. subravus. That’s probably because it has evolved an extremely specialized ecological niche — feeding and laying eggs only on the similarly rare host plant Indigofera woodii var. laxa. However, habitat fragmentation and agricultural disturbance are increasingly isolating suitable patches: work is underway to link the four remaining populations together. Source: Samways MJ & Lu S-S (2007) Key traits in a threatened butterfly and its common sibling: implications for conservation. Biodiversity and Conservation DOI 10.1007/s10531-007-9209-z

Related story in Conservation magazine: Nectar Trails of Migratory Pollinators

Image © Robert Robinson

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Jul

19

2007
 
 

Born(eo) to die



Ancient species suffer most from responsible logging, southeast Asian study shows

the tarsiers are OKAlthough well-managed, sustainable logging reduces the risk of extinction for many species, those that remain vulnerable are also likely to have the highest conservation value, according to a recent study published this week in Biotropica. A group of scientists, led by Nature Conservancy – East Kalimantan Program senior ecologist Erik Meijaard, tested a range of hypotheses in an effort to identify characteristics that could make some species more likely to vanish than others. Specialized, ancient species are less tolerant to logging than those that evolved more recently. That’s exactly the wrong way round from a conservation perspective, as older species tend to be more genetically unique than younger ones, which are more likely to have sister taxa. Well, it would be, wouldn’t it? Source: Meijaard E, Sheil D, Marshall AJ & Nasi R (2007) Phylogenetic age is positively correlated with sensitivity to timber harvest in Bornean mammals. Biotropica DOI 10.1111/j.1744-7429.2007.00340.x

Related story in Conservation magazine: Deforestation Leaves No Survivors

Image © Robert Churchill

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Jul

18

2007
 
 

NO laughing matter



Invasive tree alters Hawai’ian biogeochemical processes

a dentist's favorite plantLife’s a gas for the candleberry myrtle Morella faya, a vigorously invasive tree that’s currently rampaging through Hawai’i, New Zealand and Australia. Arizona State University biologist Sharon Hall and Stanford Carnegie coworker Greg Asner found that as the tree takes over — an innocuous understorey start to life culminates in full blown monocultural domination of the canopy — it increasingly alters nitrogen levels in the soil. Writing in Global Change Biology, Hall and Asner calculate that in just forty years since the species first arrived at the Hawai’i Volcanoes National Park rainforest, it has caused a sixteen-fold increase in nitrous oxide. This nitrogen-fixing trick effectively prevents the original species, which battled for survival in a nitrogen-poor habitat, from making a comeback. Source: Hall SJ & Asner GP (2007) Biological invasion alters regional N-oxide emissions from tropical rainforests. Global Change Biology DOI 10.1111/j.1365-2486.2007.01410.x

Related story in Conservation magazine: Nitrogen-Fixing Tree Paves the Way for Other Invaders

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Jul

17

2007
 
 

Monitoring motions: which is best?



Footprints are more reliable indicators of mink than droppings, and less messy too

Yeah. We're not so crazy about you either.American mink Mustela vison are nocturnal, elusive and devastating to European wildlife. Their secretive habits also make them difficult to monitor and most studies to date have relied on the field biologist’s favorite medium – dung – to assess how many are out there violating the local riverside. A better method, according to Oxford University biologist Lauren Harrington and colleagues, is to use “tracking rafts” – small floating platforms containing a moist clay plate to capture the mischievous mustelid’s footprints. A tasty sardine or chunk of rabbit serve as a lure. Reporting their results in the European Journal of Wildlife Research, the scientists compared the results from tracking rafts with those of a more traditional dropping count. The rafts provide a more consistent picture of mink numbers throughout the year. Now we can count them, we just need a way to get rid of them! Source: Harrington LA, Harrington AL & Macdonald DW (2007) Estimating the abundance of American mink Mustela vison on lowland rivers: evaluation and comparison of two techniques. European Journal of Wildlife Research DOI: 10.1007/s10344-007-0114-2

Related stories in Conservation magazine: Aliens Among Us | Sniffing With Precision

Image © John Pitcher

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Jul

16

2007
 
 

Get old, then fade away



Nest predation brings turtle populations to the brink in a handful of generations

ain't fading away just yetEven in a site protected for almost a century things can go very wrong for threatened species, according to a study published recently in Biological Conservation. Constance Brown and Stephen Hecnar, biologists at Lakehead University, Ontario, re-sampled turtle populations at Point Pelee National Park to see how things had changed since they were surveyed in the early 1970s. They found major differences: spotted turtles Clemmys guttata seem to have gone and Blandings turtles Emydoidea blandingii are on their way out. Only painted turtles Chrysemys picta exist there in large numbers. Shifts in age structure were also evident — the telltale signs of high nest predation, of which the healthy raccoon population bears witness. The findings show how difficult the fortunes of long-lived, slow-reproducing species can be to observe. Source: Browne CL & Hecnar SJ (2007) Species loss and shifting population structure of freshwater turtles despite habitat protection. Biological Conservation DOI: 10.1016/j.biocon.2007.05.008

Image © Steve Geer

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Jul

14

2007
 
 

High hopes for falcons



Immigrating kestrels swoop to the genetic rescue of growing population

high as a kiteEuropean populations of lesser kestrels Falco naumanni declined sharply during the middle of the twentieth century, but some are now showing signs of recovery. Such population bottlenecks, however, are notorious for reducing genetic diversity, making individuals more vulnerable to birth defects, disease and poor reproduction. Fortunately, according to a study by Joaquín Ortego and colleagues at the Instituto de Investigación en Recursos Cinegéticos, Spain, recovering kestrel populations are becoming increasingly heterozygous. Writing in Biology Letters, the scientists describe how over a six year period between 2000 and 2005, breeding pairs actually became less genetically similar. The expanding population attracts a small number of immigrants each year, adding much-needed diversity to the genetic melting pot. Source: Ortego J, Aparicio JM, Calabuig G & Cordero PJ (2007) Increase of heterozygosity in a growing population of lesser kestrels. Biology Letters DOI: 10.1098/rsbl.2007.0268

Related story in Conservation magazine: Small, Inbred, but Still Diverse

Image © Andrew Chick

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