Lee Brady's Recording Blog

Muck Better than Compost for Breeding Grass Snakes

A recently published paper in Biodiversity and Conservation has demonstrated that the grass snake hatching success is significantly affected by the medium within which eggs are deposited.

In a novel relocation experiment, Kristin Löwenborg, Simon Kärvemo, Alma Tiwe and Mattias Hagman placed grass snake eggs in different materials and monitored hatching success. Hatching success was highest in manure heaps (71%). When placed in compost piles, hatching success declined to 43%. When eggs were placed in what the authors considered to be 'natural' nests, hatching success failed completely (0%). 

 

 

The authors suggest that more stable thermal conditions within manure heaps facilitate the successful development of embryos. The decline in storage of large manure heaps on farms that adopt more modern management practices may therefore be highly detrimental to grass snakes. 

 

Time Constraints and Flexibility of Growth Strategies

We investigated geographical differences in catch-up growth strategies of populations of the common frog (Rana temporaria) from southern and northern Sweden in two factorial common garden experiments involving predation risk and two different causes of growth arrest (nutritional stress and low temperatures) to evaluate how the compensatory strategies can be affected by context-dependent costs of compensation. Larval and metamorphic traits, and post-metamorphic performance were used as response variables.

via onlinelibrary.wiley.com

 

Looks like common frog tadpoles that originate from Northern Sweden are better able to respond to changing environmental conditions than tadpoles from Southern Sweden. 

Developmental plasticity can allow amphibians to better cope with the variable hydro-periods associated with ephemeral ponds and has been demonstrated in several species (notably spadefoot toad). Plasticity may be expressed by extending the tadpole period (to metamorphose at a larger size) or by increasing the rate of development (to escape from a drying pond). This evolutionary strategy is one of the reasons why Britain's natterjack toad is able to successfully breed in the very shallow and highly ephemeral scrapes that characterise sand dunes. In a dry year, surviving toadlets may metamorphose earlier but smaller. In a wet year, toadlets may metamorphose at a larger size because they are able stay in ponds and feed for a longer period of time. Since the size of a metamorph is directly related to future breeding success, larger toadlets display higher fitness.  

What is interesting about the linked research paper is that it suggests the expression of developmental plasticity within a species may be dependent upon biogeography. 

 

How Animals Predict Earthquakes

Animals may sense chemical changes in groundwater that occur when an earthquake is about to strike.

This, scientists say, could be the cause of bizarre earthquake-associated animal behaviour.

Researchers began to investigate these chemical effects after seeing a colony of toads abandon its pond in L'Aquila, Italy, in 2009 - days before a quake.

via www.bbc.co.uk

Fascinating observations. If I notice the toads rapidly leaving ponds during next year's field season I will be heading to open ground!

 

Can Habitat Loss Prevent Amphibian Disease?

Habitat loss is generally considered to be a negative process, causing population isolation, edge effects, and extinctions. However, a new study suggests that habitat degradation can sometimes have a positive effect. Last week, a paper in PNAS showed that habitat loss may actually suppress the spread of a deadly disease in some amphibians.

via arstechnica.com

Overfished Ecosystem Held Together by a Single Species

When an ecosystem becomes overfished, some species may be able to step in and fill the food chain gaps until others can recover, according to a new study published in Science. The bearded goby, a fish that lives off the coast of southwest Africa, has become the predominant prey species in the area because the rest have been overfished. The goby should be threatened under the weight of so many predators, but it isn't—in fact, researchers find it's doing better than ever, thanks to its ability to adapt while supporting the rest of the region's food chain.

via arstechnica.com

Google Tools to Study Deforestation

In conjunction with the Copenhagen climate meeting, the search giant has demonstrated software tools that use its archive of satellite imagery to track deforestation, hoping they'll help nations prevent the liberation of the carbon sequestered in its forests.

via arstechnica.com

 

Looking forward to seeing these in action. 

Lunatic Amphibians?!

A recent paper published in the Journal of Animal Behaviour suggests that amphibian breeding may be closely linked to lunar cycles. Research by Rachel Grant, Elizabeth Chadwick and Tim Halliday found that frog and toad arrival at breeding ponds, amplexus and spawning were more likely to occur around the time of the full moon than new moon. The researchers also found that the fist sightings and peak nocturnal counts of newts were more likely to occur around the new/full moon. An outline of the full paper can be read here, with a summary also available on the BBC website. 

There are several online calculators available that allow moon phase to be calculated for a specific date. The researchers hypothesis may therefore be relatively easy to test. There are 29 Key Amphibian Sites currently listed in the KRAG database. Many of these include relatively high counts of great crested newt. I therefore thought that it may be interesting to test the theory that great crested newt counts at 10 Key Amphibian Sites will be highest around the new/full moon. 

I tested the sites using a Lunar Phase Calculator:

Site Maximum Adult GCN Count Date Moon's Age from New (Phase)

Peter's Pit 236 05/05/1995 5.7 (first quarter)

Wanshurst Green 115 25/05/2005 16.9 (waning gibbous)

Lydd Airport 103 22/04/1995 22.2 (last quarter)

Shorne Wood C.P.  70 07/06/2004 19.3 (waning gibbous)

Beacon Wood C.P.  67 04/05/1996 16.3 (full)

Well Court Farm  54 06/04/1995 25.1 (morning crescent)

T.W. Grammar School  35 31/03/2008 24.3 (morning crescent)

Pluckley 36 28/03/2007 9.7 (waxing gibbous)

Chilston Park  35 05/05/2006  7.5 (first quarter)

Barnett's Wood  20 26/04/2007 9.2 (first quarter)

For newts, we therefore want a moon age that is close to either 0, 13.5 or 27. Survey data at Wanshurst, Beacon Wood, Well Court and TW Grammar School are reasonably close (40%). Of course the results presented above are for interest only and are most certainly not statistically valid. Although newt activity will be affected by many other factors (e.g. temperature, rainfall etc), it may just be worth keeping an eye on the moon during next year's amphibian survey season.