Category Archives: Ecology

Beavers in Tidal Marshes

A cool paper came out a bit ago in one of my favourite journals, Wetlands. Why I read this journal, I’m still not entirely sure.

Beaver in Tidal Marshes: Dam Effects on Low-Tide Channel Pools and Fish Use of Estuarine Habitat

Beaver (Castor spp.) are considered a riverine or lacustrine animal, but surveys of tidal channels in the Skagit Delta (Washington, USA) found beaver dams and lodges in the tidal shrub zone at densities equal or greater than in non-tidal rivers. Dams were typically flooded by a meter or more during high tide, but at low tide they impounded water, allowing beaver to swim freely while quadrupling pool habitat for fish compared to channels without dams. Seven fish species were caught in low-tide pools, including threatened juvenile Chinook salmon (Oncorhynchus tshawytscha), whose densities (by volume) averaged 3.2 times higher in low-tide pools than shallows. Accounting for the total contribution of pools and shallows to juvenile Chinook abundance, beaver pools tripled shrub zone channel capacity for juvenile Chinook salmon at low tide relative to herbaceous zone marsh without beaver pools. Current Chinook recovery efforts focus on restoring herbaceous zone tidal marsh for rearing juveniles, but this focus overlooks presently rare and poorly understood habitat, like tidal shrub marsh, that was historically common and likely important to beaver and small estuarine or anadromous fish.

Without going to deep into analysis, I wonder what this might mean for Scottish beavers. The Scottish salt marshes haven’t done well in the land reclamation wars (not actual wars), but they still represent 13.7% of Great Britain’s total amount of salt marshes (probably so low due to the Fens and other large estuaries in the south.) American beavers, such as the ones studied above on the Skagit, build bigger dams, and so might be more able to make use of salt marshes – but it is also possible that Scottish beavers might be able to help out with the local fisheries. Idle speculation, however, as the SNH has repeatedly shown no care for their now native beaver population that were established illegally.

The Raccoon Dog in Europe

The raccoon dog Nyctereutes procyonoides is an East Asian basal canid (meaning that it resembles proto-dogs, basically.) It has no relation to the raccoon, and only marginally to the dog. It’s the only canid to hibernate, has a varied omnivorous diet, likes to live near or around marshes, and can climb trees. You’ve probably heard about it as a fur species – it commonly comes up an the radars of environmental animal defenders as the kind of species we shouldn’t be getting fur from in China, mostly because it is easier to skin the animal alive than it would be to kill it first. Here’s a cute picture to make that thought sink in.

The species has been introduced into Western Europe, where it is currently being treated as an invasive species. There’s been a flurry of invasive species literature and discussion going about currently, especially on the ECOLOG email list, and Current Zoology recently did a special issue journal comprised of papers about the topic. Two of those papers were on the Raccoon dog. I read them recently, and here are a few of my comments. (Note to journal editors – two spelling errors in the introduction doesn’t make the reader want to read your journal.)

ResearchBlogging.orgI suggest reading both of the articles, themselves. This post is more an attempt at seeing if note-taking online will help me understand how I react to and read journal articles better, and whether open discussion will help the topic or not. Most research blogs come at the reader with an attitude of “I know more than you, so I’ll use simple words to talk about this interesting new study.” I hope that this isn’t the case here – I know less, so here is my understanding and my questions.

Invasion of the raccoon dog Nyctereutes procyonoides in Europe: History of colonization, features behind its success, and threats to native fauna (File)

by Kaarina KAUHALA, Rafal KOWALCZYK

This was a fairly good overview of the raccoon dog. The article seemed mainly to be comprised of a vast literature search and a summing up of what the racccoon dog is doing in and to Europe. There were multiple introductions of >9000 animals (mostly for fur and game), which means that it started with a very strong hold. There’s still scarce actual studies on how the raccoon dog is affected systems, mostly because it is difficult to do quantificational studies across a region of a certain species alone. But to give a picture of how good it is at reproducing and becoming part of a region’s ecology – the hunting bag for Finland went from 818 in 1970 to 172,000 in 2009. The raccoon dog increases it’s range at a rate of over 40km per year, but that doesn’t take into account where it manages to grow in density. In some parts, it can be as common as 2 raccoon dogs per square kilometre. They’ve now reached southern Spain, so their population should be growing more dense instead of much more outward over the next 50 years.

The success of the raccoon dog invasion in Europe was enabled thanks to an exceptional combination of factors including: widely distributed and multiple introductions, great migratory ability and the high reproductive capacity of the species, plasticity of food habits, hibernation in areas where climate is harsh and its general adaptability to different climatic and environmental conditions, and the admixture of individuals from divergent matrilineages. pp. 594

This quote is particularly interesting if you consider how the official beaver is faring in Scotland – it is being introduced on a very limited range with no genetic variation, it can’t each much, the Nordic ‘official’ beavers seem to struggle in winter, and it doesn’t reproduce large litters. And it shows, especially compared to the illegal Bavarian beavers up north on the Tay.

The paper then talks about the diet, the size of the litter (maximum of 16, which is pretty big), the effect on native wildlife. There’s very little proven as to whether the raccoon dog has actually damaged the local ecosystems – however, it is clear that foxes have become more carnivorous, and less in number. This may be because the raccoon dog, like the American dog, can eat pretty much anything. Badgers don’t like nesting with them, but the raccoon dog likes to breed in active badger sets. The fact that badgers sometimes kill the young doesn’t really discourage them (and as the badgers don’t breed while their house is occupied by a raccoon dog, the issue goes away eventually anyway.)

There’s then a lot of focus on the raccoon dog as a vector for disease and parasites – something it seems to be quite readily. There are more diseases reported in foxes where there are a lot of raccoon dogs, which suggests that it is a reservoir for all sorts of zoonosis.  But at this point, that’s basically the end of the article. It was a good summary.

Estimated prevalence of Echinococcus multilocularis in rac-coon dogs Nyctereutes procyonoides in northern Branden-burg, Germany (File)

by Sabine SCHWARZ, Astrid SUTOR, Christoph STAUBACH, Roswitha MATTIS, Kirsten TACKMANN, Franz Josef CONRATHS

So, Human Alveolar Echinococcus is a lethal disease in humans if left untreated. It affects over 18,000 a year – but 91% of those are in China, which says a lot about Chinese health. 25 cases are reported each year in Germany, but that is probably very low compared to actual cases. Basically, AE is a disease that comes from the tapeworm, involves the multiplication of cysts in the body, and it is isn’t pretty. I’d link to the Wikipedia article, but I am writing this article over lunch, and I’ve suddenly stopped eating.

This article was a study, along with the standard literature review and coverage of the disease in Europe, especially in the traditional host the red fox, and a covering of the raccoon dog as an invasive species. The authors then looked at 161 raccoon dog carcasses collected from local hunting bags in Northern Germany and checked these for incidents of AE or tapeworms. They then ran some Bayesian stats to calculate the probable amount of infected raccoon dogs in the area. They did find some raccoon dogs that were infected, but, as they admit, it’s hard to say whether this means that the raccoon dog is causing more incidents of AE in Europe, or whether it means more transmissions to humans. All in all, the study seems to suggest that yes – raccoons can get AE and transmit it to foxes. And that’s about it. Still, an interesting study, and I look forward to future work from these authors.

And I guess that’s it.

References:

Sabine SCHWARZ, Astrid SUTOR, Christoph STAUBACH, Roswitha MATTIS, Kirsten TACKMANN, Franz Josef CONRATHS (2011). Estimated prevalence of Echinococcus multilocularis in raccoon dogs Nyctereutes procyonoides in northern Brandenburg, Germany Current Zoology, 67 (5), 655-661
Kaarina KAUHALA, Rafal KOWALCZYK (2011). Invasion of the raccoon dog Nyctereutes procyonoides in Europe: History of colonization, features behind its success, and threats to native fauna Current Zoology, 57 (5), 584-598

Rssd: Carvings in Timor, Arctic Climate Predictions, & Seahorses

From now on, any article I start with Rssd will mean RSS feed dump. Meaning, I’ve read these articles, but I don’t have much to say about them, otherwise.

Quest for extinct giant rats leads scientists to ancient face carvings

ScienceDaily (2011-02-11) – Ancient stone faces carved into the walls of a well-known limestone cave in East Timor have been discovered by a team searching for fossils of extinct giant rats.

This is pretty interesting. On the one hand, they were looking for giant rats. On the other hand, they found faces dating back 12,000 years. It doesn’t state that they found the cave – they’ve known about human habitation and wall art going back 30,000 years for over fifty years now in Lena Cave. What’s interesting is that they found now ones from the Pleistocene age. I’m pretty interested in human migrations in the area, so it’s cool to know this sort of stuff.

Arctic climate variation under ancient greenhouse conditions

ScienceDaily (2011-02-11) — Tiny organisms preserved in marine sediments hold clues about Arctic climate variation during an ancient episode of greenhouse warming. [...]

Based on reconstructions of Arctic climate variability in the greenhouse world of the Late Cretaceous, Southampton scientists have concluded that man-made global warming probably would not greatly change the climatic influence associated with natural modes of inter-annual climate variability such as the El Niño — Southern Oscillation (ENSO) or the Arctic Oscillation/ North Atlantic Oscillation (AO/ NAO). [...]

It is anticipated that the Arctic Ocean will become ice free during the summer within the next 15-50 years as a result of global warming. Because sea ice is reflective, its loss will reduce the amount of the Sun’s energy bounced back out to space, thereby amplifying regional warming. However, changes in atmospheric circulation could also occur, making it difficult to unravel the likely net effect on climate.

This is an interesting article. Professor Alan Kemp (and others) of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre, Southampton analysed Artic sediment cores for phytoplankton, and used those to conclude that a permanent El Niño is unlikely. Good to know.

How the seahorse got its shape

Hypothesis: form and function evolve hand-in-hand: compared to their close relatives, the straight-bodied pipefishes, seahorses’ unique curved shape provides them with increased feeding efficiency

This is pretty damn interesting. All I really have to say about that. I do love me some pipe-fish, I used to catch them in the Cape Cod bay with nets when I was younger.

Davies, A., Kemp, A., & Pälike, H. (2011). Tropical ocean-atmosphere controls on inter-annual climate variability in the Cretaceous Arctic Geophysical Research Letters, 38 (3) DOI: 10.1029/2010GL046151

On Rogue Beavers in Scotland

From: http://www.guardian.co.uk/environment/2010/nov/25/beavers-scotland-conservation on 02-12-2010: 1:26am

From: http://www.guardian.co.uk/environment/2010/nov/25/beavers-scotland-conservation on 02-12-2010: 1:26am

ResearchBlogging.orgThe European Beaver (Castor fiber) unfortunately became extinct in Britain in the 1500s. It was widely hunted for both its fur, castoreum (an excretion from the animal’s castor sack scent glands), and for its meat – oddly, the Church classified it as a fish, which meant it could be eaten on Fridays. There haven’t been significant beaver populations in Britain, if any at all, for over 400 years.

Over the past ten years there have been various attempts at reintroduction into Scotland. According to Scottish Natural Heritage, this is because “The beaver is a charismatic species which would serve to raise wider biodiversity issues such as riparian woodland management, aspen restoration, wetland biodiversity and dead wood habitat.  There are few species which have such significant influences on ecosystem function and health.” The beaver is also adequately described as a ‘keynote species,’ which means that they help support the ecosystem they’re in. This means that they influence the environment in a variety of ways which are not immediately clear – for instance, their impoundments help to increase the stability of water levels, which leads to an increase in riparian grasses, which are the food of the water vole (Arvicola terrestrisis). (Gurnell et al., 2009)

In 2009, a trial reintroduction was started in Argyll. Three families were released into the Knapdale forest. As many as ten different organisations are monitoring the beavers in their once-native environment. The preparation was significant – a year passed before the approved permit for reintroduction was actually acted upon, and the AOC Archaeology group did an extensive survey of the Loch Coille-Bharr Crannog before the introduction. (Cavers, 2009) In charge of the entire operation, however, is the Scottish National Heritage. They’ve been doing quite a bit of research into beavers over the past few decades. But research isn’t their main interest: according to their web page, their ”purpose is to:

  • promote care for and improvement of the natural heritage
  • help people enjoy it responsibly
  • enable greater understanding and awareness of it
  • promote its sustainable use, now and for future generations.

All our work supports our mission: All of nature for all of Scotland.

So, what’s interesting isn’t the reintroduction of the mammal – the first time this has been done legally in the UK – into Scotland, nor the trial period which is currently successfully underway.  Rather, the SNH’s behaviour towards a score of rogue beavers is sure to raise eyebrows.

Basically, over the past few years a score or so of beavers have been seen around Scotland, particularly on the Tay. The actual number is in doubt: some estimate as low as six rogue beavers are present in Scotland, while others posit the number could be as high as 50. They are breeding – at least one pair has two kits. These animals either escaped from private collections or were introduced purposefully and illegally (without a suitable permit.) The SNH is dedicated towards trapping and removing these beavers from the wild. One of the many articles on the issue (which I’ll not link again in the rest of the article, but from where most of the following information comes) states that the SNH said the following concerning it’s plans:

“They are being recaptured because their presence in the wild is illegal and because their welfare may be at risk,” a spokesman said. “There was no consultation with local people; there was no licence issued for their release; there is no monitoring of their welfare; and there is no certainty that they are the appropriate species or type of beaver for Scotland.” That claim was contested by Lister-Kaye, a former chairman of SNH’s Highland regional board, and by Ramsay. They said their beavers were Bavarian and from a much stronger and more varied genetic stock than the Norwegian beavers released at Knapdale.”

This is markedly odd. First, their welfare is not necessarily at risk. There is no indication anywhere that they are at risk – the fact that they are breeding and building dams alone suggests the opposite. Secondly, there was consultation with the local people regarding beavers in general: 59% are in favor of their reintroduction. Thirdly, while there may be no monitoring of their welfare, that is no reason to remove them from the wild. Merely monitoring the beavers would be enough to clear up most of the supposed issues. However, it’s been stated in the articles that there are no suitable zoos or holding facilities which will adequately be able to take this amount of beavers – and this will most likely lead to having to put the animals down. (As well as possibly leaving the few kits on their own, if they are not trapped successfully.)

As for the certainty of stock – the beavers introduced by the SNH are not necessarily better than those in the wild. According to an independant post on the Facebook Group set up by members of the public to save the beavers from capture, it’s stated that:

“A row of distinguished naturalists think the Bavarian beaver – or any European beaver – is quite acceptable for Scotland. Norwegian ones used in the official trial come from an inbred population which seems to have a tendency to genetic faults such as only having one kidney. The death rate for the reintroduction was unexpectedly high. Beavers, reintroduced to Bavaria in the 20th century, were intentionally hybridized from several of the remnant populations to create a robust group from which to found a strong population.”

If that’s not a good argument for allowing them to continue to exist, than I’ll find my old beaver-skin hat and eat it (not really. I am vegetarian, for one.) As well, there is no reason to trap and remove the beavers to ascertain if they are in fact of better stock (which they seem to be).

So why are the SNH removing the beavers? The Guardian suggests that it’s because they’re simply the wrong beavers. The SNH has one a lot of background work trying to get beavers reintroduced in the first place, and they don’t seem to be able to deal with the fact that a few errant beavers are able to do this for themselves. The way they are trapping them, as well – in particular, using local volunteers (probably land owners), and disallowing their communication with the media – is very sneaky and questionable. Even more odd is the fact that the SNH’s official position is that ”the fact remains that leaving these animals in the wild would mean choosing to ignore well-established wildlife legislation. This is not something that SNH, or any other government organisation, can do.”

Reynolds (2000) did argue that there ought to be contingency plans in place in case of unmonitored populations overexploiting local resources, but said himself that “No reports of nationally significant economic or ecological beaver-induced damage to woodlands were found,” although that may be different for such sites as the historically significant crannog the beavers were introduced to in Argyll. The SNH may simply be acting on these supposed contingency plans. They may be also trying to get the same sort of local help that was received tracking down American Mink in Scotland, as documented here and in Bryce (2010), which is a predator of the previously mentioned water vole and managed to reduce its range considerably. But the beaver is not such a disruptive species, and if anything benefits local ecosystems, as the SNH has themselves admitted.

So, on what grounds are the SNH trapping and removing these animals? It must merely be the license which wasn’t granted for them. As already stated, there are other ways of monitoring the current rogue populations besides trapping and removal. But, in summation, I completely agree with Mike Leahy, the Rocky Mountain regional director of a private group, Defenders of Wildlife, who said, concerning the proposed delisting of grizzlies and wolves as endangered, that ”Wildlife management decisions are supposed to be made based on science, not politics.” This is not being done here.

References:

  • Cavers, G. (2009). Loch Coille-Bharr Crannog Condition Survey. AOC Archaeology Group, www.aocarchaeology.com.
  • Gurnell, J., et al.(2009). The feasibility and acceptability of reintroducing the European beaver to England. Natural England, http://naturalengland.etraderstores.com/NaturalEnglandShop/NECR002.
  • Reynolds, P. (2000). European Beaver and Woodland Habitats: A Review. Scottish National Heritage Review, London.

Research Blog References:
Bryce, R., Oliver, M., Davies, L., Gray, H., Urquhart, J., & Lambin, X. (2010). Turning back the tide of American mink invasion at an unprecedented scale through community participation and adaptive management Biological Conservation DOI: 10.1016/j.biocon.2010.10.013

Mung! (Or Pylaiella and Macroalgal Blooms)

Pylaiella LittorisThis post was chosen as an Editor's Selection for ResearchBlogging.orgMung is the colloquial name on the NE coast of the US for pylaiella littoris, a common seaweed. Don’t worry if you haven’t heard the name; as far as I’m aware, it’s a fisherman’s term that doesn’t have large usage outside of the small, local communities in places like Cape Cod. For examples, see here, here, here, and here.

ResearchBlogging.orgI’ve been vacationing there since I was six, and spent a summer or two working there, as well as more than a few visits outside of peak season. Each year, the mung seems to get worse. I’m not alone in thinking this. Seaweed is normally not a problem for coastal tourists – indeed, a strong population of seaweed is necessary for a healthy coastal ecosystem. Mung, however, tends to float in in the later months of the summer, particularly August, and clogs up the beaches with swathes of reeking, brown algae (in Cape Cod, at least. It occurs on a global scale.) This isn’t necessarily a new thing, however; Thoreau wrote about it in his book on Cape Cod, calling it ‘Monkey hair’. But in my search to find out if my suspicions are correct, that algal blooms are increasing in intensity in the North Atlantic, I ran across an article by Patrick Lyons, Carol Thornber, John Portnoy, and Evan Gwilliam, paid for by the National Park Sevice, which dealt with that specifically. Here’s the abstract:

“Accumulations of nuisance drift macroalgae along the open-coast Atlantic beaches of the Cape Cod National Seashore have been observed on an anecdotal basis for over 50 years. This entire stretch of coastline is sandy, with no solid substrata for algal attachment. During the summer of 2006, we collected data on drift macroalgal accumulations repeatedly throughout this National Seashore. Peak biomass (primarily consisting of filamentous red algae and Ulva lactuca) was found in early August, primarily at the northernmost site. Our data, together with current patterns and anecdotal evidence suggest that macroalgae may originate in rocky shorelines of northern New England and are transported south by Gulf of Maine currents. Algae are most likely caught along the Cape Cod National Seashore shoreline by sand bars, particularly in the northern part of the shoreline.”

I had never suspected that the mung came from the north, or indeed that it was carried over distances at all. Although, I should have suspected as much, as the mung proliferations were very noticeable on the ocean-side, which lacked any sort of ‘solid substrata’, being entirely clean sand as far as I had ever swum.

But why does it come, at all? Nitrogen is the most common reason I’ve found on the net. The study, done in 2006, found that “Blooms typically peak in late summer (e.g. Berglund et al. 2003), due to light levels, nutrient levels, water temperature, and other factors associated with seasonality. We found that algal abundance along the [Cape Cod shore] did peak in August. However, on smaller temporal and spatial scales, drift macroalgal biomass was quite patchy. We found a significant negative relationship between algal density and [dissolved inorganic nitrogen] concentration, implying that algae are likely using nutrients to proliferate while drifting, and their growth may be nutrient-limited in dense aggregations. However, subtidal drift macroalgae did not only occur in dense aggregations, and these aggregations only occurred occasionally.” (Lyons et al., 2009: 6)

This means, effectively, that it is difficult to pin down a single variable for macroalgal blooms in the studied area. Simply put, more study is necessary, especially as “macroalgal blooms also have important ecosystem functions such as providing habitat for invertebrates (Hull 1987, Norkko et al. 2000) or fish (Kingsford 1995), and food for herbivorous grazers (Salovius and Bonsdorf 2004). In addition, blooms may indirectly cause hypoxic or anoxic conditions upon decomposition (Raffaelli et al. 1998); they also have been associated with decline of corals (Bell 1992) and seagrasses (Peckol et al. 1994) due to competition for nutrients and/or shading” (Lyons et al., 2009: 1) And, according to the local lobster fishermen, the mung can get so bad as to weigh down lines and lose traps.

However, the report failed to look beyond the “bottom-up” assumption – “that is, that physics, nutrients, and other non-biological factors determined where marsh plants grew or did not grow.” (As mentioned in another article on Cape Cod, this time on marshes and cord-grass reduction.) I’m not well-versed enough in this to say much at this point, but various other articles have suggested that the physical properties of the environment may not be the only things at work. For instance, another report “concluded that the relative effects of grazers and nutrient enrichment depended on the nutrient status of the system, algal life history strategy, and season. Strong bottom-up and top-down controls shape benthic community composition before macroalgae reach visible size.” (Lotze, Worm, & Sommer 2001) I wonder what sort of implications this might hold for mung blooms…

References:

  • Hull, S.C. 1987. Macroalgal mats and species abundance: A field experiment. Estuarine, Coastal, and Shelf Science 25:519–532. CrossRefCSA
  • Kingsford, M.J. 1995. Drift algae: A contribution to near-shore habitat complexity in the pelagic environment and in attractant for fish. Marine Ecology Progress Series 116:297–301. CrossRef,CSA
  • Lotze, Heike K., Boris Worm, Ulrich Sommer. 2001. Strong Bottom-Up and Top-Down Control of Early Life Stages of Macroalgae. Limnology and Oceanography, Vol. 46, No. 4 (Jun., 2001), pp. 749-757.
  • Lyons, Patrick | Thornber, Carol | Portnoy, John | Gwilliam, Evan. Dynamics of Macroalgal Blooms Along the Cape Cod National Seashore. Northeastern Naturalist [Northeast. Nat.]. Vol. 16, no. 1, pp. 53-66. Mar 2009.
  • Norkko, J., E. Bonsdorff, and A. Norkko. 2000. Drifting algal mats as an alternative habitat for benthic invertebrates: Species-specific responses to a transient resource. Journal of Experimental Marine Biology and Ecology 248:79–104. CrossRefPubMed
  • Peckol, P., B. DeMeo-Anderson, J. Rivers, I. Valiela, M. Maldonado, and J. Yates. 1994. Growth, nutrient uptake capacities, and tissue constituents of the macroalgae Cladophora vagabunda andGracilaria tikvahiae related to site-specific nitrogen loading rates. Marine Biology 121:175–185.CrossRefCSA
  • Raffaelli, D.G., J.A. Raven, and L.J. Poole. 1998. Ecological impact of green macroalgal blooms.Oceanography and Marine Biology 36:97–125. CSA
  • Salovius, S., and E. Bonsdorff. 2004. Effects of depth, sediment, and grazers on the degredation of drifting filamentous algae (Cladophora glomerata and Pilayella littoralis). Journal of Experimental Marine Biology and Ecology 298:93–109. CrossRef

Research Blog References:
Bell, P. (1992). Eutrophication and coral reefs—some examples in the Great Barrier Reef lagoon Water Research, 26 (5), 553-568 DOI: 10.1016/0043-1354(92)90228-V