Inspired by Nature: A Poem of Return
Froglife’s Communications & Fundraising Officer, Ashlea Mawby, felt inspired by the work she does here at Froglife and wrote this poem.
Inspired by Nature: A Poem of Return
Froglife’s Communications & Fundraising Officer, Ashlea Mawby, felt inspired by the work she does here at Froglife and wrote this poem.
Hot Weather Warning – Amphibians & Reptiles
After a cold start to the year, with weather events such as the ‘Beast from the East’, many people are enjoying the sizzling heat and sun that has now arrived in the UK. It is important to note that these extreme temperatures pose a risk to some of our UK wildlife. Our UK amphibian species struggle in high temperatures, particularly the tiny froglets and toadlets that are just emerging from their tadpole phase.
The most obvious and useful way to help these animals is to #BuildAPond, giving these animals and other wildlife ready access to water, for drinking and bathing. But building a pond doesn’t have to be a big nor expensive endeavour, and small ponds (e.g. bucket-sized) can be just as effective. Read more about building a pond with our FREE online guide Just Add Water.
In these heat extremes, a quick 2-minute job of putting out a small container or dish filled with fresh water will also help wildlife in your garden. If it’s a deep dish, don’t forget to add in a ramp or some stones to allow any animals that may fall a way to climb out. It is best to fill with water from a water butt rather than the tap, if you have one.
Frogs, Toads, Birds and Hedgehogs all eat small invertebrates like worms, which in this hot weather burrow deeper down into the dry soils. With this in mind, it is important to keep plants and soils damp to allow the predators to access their vital food source.
In addition to adding water into your outdoor space, keeping areas wild and sheltered can potentially save amphibian lives. Rockeries and log piles both provide shade to amphibians in the garden, where often the soil beneath will remain damp and the temperature much cooler that the outside.
Even the reptiles, like common lizards and grass snakes that can often be found basking in the sun, need shaded areas for relief from high temperatures. So log piles and rockeries are equally important for these animals to escape from the sun’s rays.
eDNA for detecting great crested newts – a replacement for traditional survey techniques?
Environmental DNA, or eDNA, is released by most organisms as they occupy different habitats. Each species has a unique type of eDNA which can be recognised through laboratory analysis. This provides a novel tool for detecting species within the environment. Sources of eDNA may originate from sloughed skin or hair, eggs, faeces and saliva (Figure 1). Within aquatic habitats, most organisms release eDNA into the surrounding water. An increasing number of methods are now available for detecting the eDNA of a range of aquatic organisms including fish, damselfly nymphs, crustaceans and amphibians. In recent years, techniques have advanced to allow the detection of eDNA of great crested newts from their breeding ponds. This has proved particularly useful for ecologists and voluntary surveyors who need to determine the presence or absence of great crested newts for the purposes of conservation and mitigation. The eDNA technique, though expensive, is usually highly reliable and effective at detecting great crested newts. Research carried out by Biggs et al. (2015) of 35 ponds in Hampshire and Wales showed that eDNA could successfully detect the presence of great crested newts in 99.3% of ponds. This was significantly higher than the success rate of more traditional survey techniques.
Traditional survey techniques for detecting great crested newts such as egg-searching, night torching and bottle trapping are labour intensive, carry certain risks (e.g. potential suffocation of newts in traps) and are not always highly effective. Biggs et al. (2015) found that bottle trapping detected great crested newt presence in 76% of ponds and egg searching in only 44% of visits. Using traditional survey techniques, Natural England advice recommends four visits to a breeding pond in the newt breeding season (mid-March to mid-June) using a minimum of three traditional survey techniques (Natural England, 2015) (Figure 2). The eDNA technique, by contrast, can detect great crested newts on just one visit with minimal disturbance to breeding ponds (Biggs et al., 2015). Therefore, should eDNA replace traditional surveys techniques to detect great crested newts? In this article we highlight the relative advantages of disadvantages of eDNA and point out the limitations that ecologists and voluntary surveyors need to be aware of when using the technique.
One of the major advantages of eDNA is the relative ease that samples can be taken from a pond and the subsequent reduction in labour costs. For example, one fieldworker may be able to take samples for analysis within one survey visit, compared to the multiple sessions required using traditional survey techniques. However, the analysis costs associated with eDNA may be significant, especially if carrying out many samples. A second major advantage of eDNA is its overall reliability compared to other traditional methods. However, a range of studies have found variations in the success of eDNA, ranging from 60% to 99% (Buxton et al., 2017a).
Despite is apparent reliability and success in detecting great crested newts, there are a number of limitations of using eDNA to survey ponds. Six of the main limitations are outlined below:
Overall, although using eDNA to detect the presence of great crested newts is highly effective and usually reliable, ecologists and surveyors must be aware of the potential limitations when carrying out surveys. Therefore, caution should be taken when analysing the results from eDNA; ecologists and surveyors should consider eDNA as an additional technique to complement traditional survey methods, rather than being viewed as replacing existing techniques. We conclude this article with a statement by Rees at al. (2014a): “Environmental DNA methodologies should not be used to replace or disregard the knowledge and expertise of experienced field ecologists and taxon specialists, but should become an important tool to enhance limited conservation resources”.
Biggs, J., Ewald, N., Valentini, A., Gaboriaud, C., Dejean, T., Griffiths, R.A., Foster, J., Wilkinson, J.W., Arnell, A., Brotherton, P., Williams, P. & Dunn, F. (2015) Using eDNA to develop a national citizen science-based monitoring programme for the great crested newt (Triturus cristatus). Biological Conservation, 183: 19–28.
Buxton, A.S., Groombridge, J.J., Zakaria, N.B. & Griffiths, R.A. (2017) Seasonal variation in environmental DNA in relation to population size and environmental factors. Science Reports, 7: 46294; doi: 10.1038/srep46294.
Buxton, A.S., Groombridge, J.J. & Griffiths, R.A. (2017a) Is the detection of aquatic environmental DNA influenced by substrate type? PLoS ONE, 12 (8): e0183371.
Bohmann, K., Evans, A., Thomas, M., Gilbert, P., Carvalho, R., Creer, S., Knapp, M., Yu, D.W. & de Bruyn, M. (2014) Environmental DNA for wildlife biology and biodiversity monitoring. Trends in Ecology & Evolution, 29 (6): 358-367.
Natural England (2015) Great crested newts: surveys and mitigation for development projects. https://www.gov.uk/guidance/great-crested-newts-surveys-and-mitigation-for-development-projects#when-to-survey. Accessed 20th June 2018.
Rees, H.C., Bishop, K., Middleditch, D.J., Patmore, J.R.M., Maddison, B.C. & Gough, K.C. (2014) The application of eDNA for monitoring of the Great Crested Newt in the UK. Ecology and Evolution, 4 (21): 4023–4032.
Rees, H.C., Maddison, B.C., Middleditch, D.J., Patmore, J.R.M. & Gough, K.C. (2014a) The detection of aquatic animal species using environmental DNA – a review of eDNA as a survey tool in ecology. Journal of Applied Ecology, 51: 1450–1459.
Rees, H.C., Baker, C.A., Gardner, D.S., Maddison, B.C. & Gough, K. (2017) The detection of great crested newts year round via environmental DNA analysis. BMC Res Notes, 10: 327. DOI 10.1186/s13104-017-2657-y.
Thomsen, P.F. & Willerslev, E. (2015) Environmental DNA – An emerging tool in conservation for monitoring past and present biodiversity. Biological Conservation, 183: 4–18.
The end of the Scottish Dragon Finder project is now upon us and the last four and a half years have been filled with many activities seeing tens of thousands of people throughout Scotland learning more about amphibians and reptiles and volunteering their time to help our species. The Scottish Dragon Finder team ran over 250 sessions engaging over 33,000 people throughout the project. Also 70 habitats were created or restored as part of the project. Scottish Dragon Finder impacted far and wide across Scotland working across 31 of the 32 council areas.
On the 9th June a talk on Scottish Dragon Finder was given at the Glasgow Science Festival Conference (Amphibians and Reptiles of Scotland: current research and future challenges) at the University of Glasgow. The conference was well attended in Glasgow’s tropical weather conditions and the talk, providing an overview of the project, was well received with positive feedback.
Staff completed site visits to the final 10 sites across Scotland, gathering data on the ponds and checking their condition before finishing our reports. Aerial footage was recorded at many of the sites too which can be put together soon to see the ponds from a different perspective.
Our last event took place at Rouken Glen Park in East Renfrewshire as part of World Environment Day. Along with East Renfrewshire staff and other charities, Scottish Dragon Finder hosted a stall and ran pond-dipping at the park’s pond with many enthusiastic families!
Many thanks to our funder, Heritage Lottery Fund, for funding Scottish Dragon Finder and all the other funders who contributed towards the project’s successes. A big thanks to all those who volunteered their time on Scottish Dragon Finder, helping us accomplish so much since 2014.
Kin recognition – when recognising relatives is important
During the spring in temperate countries tadpoles of frogs and toads often develop in a range of water bodies from small ponds to lakes. Swimming around in the open water, tadpoles are highly vulnerable to predation so in many species such as the common toad (Bufo bufo), tadpoles swim in large groups or shoals (Figure 1). By living in groups the tadpoles gain advantages such as decreased risks of predation and increased access to food. However, there are costs to group living such as an increase in the risk of transmitting infectious disease and intraspecific competition. Research has shown that tadpoles further increase the benefits of group living by associating with relatives, or close kin. If forming shoals reduces the risk of predation, then swimming with relatives who possess similar genes will increase the chances that these genes will survive to the next generation. The exact mechanism of kin recognition in anuran tadpoles is not clear but studies suggest that frog and toad tadpoles recognise each other through chemical cues (Eluvathingal et al., 2009). The persistent dense swimming shoals of tadpoles of many amphibians from the genera Rana and Bufo (e.g. wood frog (Rana sylvatica); common toad (Bufo bufo); and boreal toad (Bufo boreas)) have been shown to consist primarily of associations of closely related kin (Blaustein & Waldman, 1982). However, in the red-legged frog (Rana aurora), Schneider’s toad (Duttaphrynus scaber) and Günther’s golden-backed frog (Indosylvirana temporalis), tadpoles only exhibit kin recognition early in their development when they form dense shoals. As they mature, tadpoles disperse and kin recognition drops (Rajput et al., 2014). During late development the risks of pond desiccation are high and individual tadpoles seek isolated patches of water. Under these conditions the risks of suffocation through desiccating water is higher than the benefits of associating with relatives. Further to this, recent research has shown that the persistence of associating with kin varies considerably even within a single species. For example, larvae of the wood frog (Rana sylvatica) from North America exhibits kin recognition and individuals often choose to swim with relatives. However, Halverston et al. (2006) have shown that the level and occurrence of swimming with relatives is not consistent but depends on a range of factors including levels of competition, predation and parasitism. Tadpoles from two adjacent ponds exhibited different levels of association with kin due to localised differences in these factors (Halverston et al., 2006). This demonstrates that associating and swimming with relatives only occurs under certain environmental conditions and groups of tadpoles may show variations in their degree of kin association.
Many amphibians within temperate zones are herbivorous, however there are a number of tropical species of tadpole which are carnivorous. This provides the opportunity for cannibalism to evolve where larger tadpoles may predate smaller ones within the same species. In these species it may be advantageous for tadpoles to recognise kin to avoid potential predation on relatives who carry the same genes. Research has shown that cannibalism generally occurs when the nutritional benefits gained from eating relatives outweigh the disadvantages such as risks of injury, transmitting infectious diseases and losing potential members of the same species who carry similar genes. As a result, cannibalism has evolved in some carnivorous amphibian larval species, but not others, depending on the environmental conditions and the relative advantages and disadvantages of consuming close kin.
Many tropical frogs in the genus Dendrobates lay their eggs in terrestrial habitats that are then transported by males to small water-filled water bodies formed in the axils of tree leaves (phytotelmata). Females of the poison dart frog Dendrobates auratus only lays a few eggs per year, so the number of tadpoles developing within any given water body is low. In some species of Dendrobates frogs, the female lays non-fertile eggs into the water to feed the tadpoles. However, female D. auratus does not perform this behaviour so the tadpoles rely completely on external food sources e.g. fallen insects, for survival. Starvation within such small water bodies is very high and therefore cannibalism has evolved to allow some of the tadpoles to survive. In this species the larger tadpoles predate the smaller ones which provides additional nutrition which is crucial for survival. However, male D. auratus may bring tadpoles from a number of clutches so there is also the potential for kin recognition i.e. larger tadpoles may choose to consume non-relatives over relatives since the latter may share the same genes. However, experiments carried out by Gray et al. (2009) suggest this is not the case and that larger tadpoles indiscriminately predate kin from non-kin. The authors hypothesise that since food sources are so scarce for developing tadpoles then the benefits of individual survival outweigh the costs of losing genetic relatives.
Additional research by Poelman & Dicke (2007) has shown that in the poison dart frog Ranitomeya ventrimaculata, females exhibit a plasticity in where she lays her eggs, which depends on environmental conditions (Figure 2). In this species, like D. auratus, tadpoles are highly cannibalistic, consuming both kin and non-kin. At the beginning of the breeding season, when water-filled phytotelmata do not contain many tadpoles, the female will spread her eggs widely amongst different water bodies, avoiding those which already contain a tadpole. This reduces the chances that her eggs will get consumed by another tadpole (which may or may not be her own). However, nearer to the end of the breeding season, the female changes behaviour and actively starts laying more eggs in phytotelmata which already contain large tadpoles. Poelman & Dicke (2009) hypothesise that this is because at the end of the breeding season there are few free phytotelmata left and by provisioning those that already contain tadpoles with fertilised eggs, she is providing food to the tadpoles which may be her own. This sacrifice of eggs will indirectly improve the survival of her existing tadpoles, the eggs of which she laid early in the breeding season. This plasticity in behavioural response allows a greater number of tadpoles to survive when the risk of desiccation of water bodies is high.
The green and golden bell frog (Litoria aurea) was once a common species widely distributed in south eastern Australia (Figure 3). It has also been introduced into New Zealand and surrounding islands. However, the extreme sensitivity of these species to the infectious chytrid fungus has been the major cause of the species’ decline in its native range and the species is currently restricted to small isolated populations. The tadpoles form groups where individuals gain protection from predators, increased foraging efficiency and better growth. Associating with relatives is advantageous since individuals would be indirectly protecting those carrying similar genes. Pizzatto et al. (2016) examined the behaviour of tadpoles of the green and golden bell frog in relation to kin recognition. The authors found that in the bell frog L. aurea tadpoles did indeed distinguish kin from non-kin and thus formed shoals containing mainly relatives. The authors suggest the advantages to this species include increased growth and increased resistance to disease since related members are likely to carry the same disease resistance genes.
Blaustein, A.R. & Waldman, B. (1982) Kin recognition in anuran amphibians. Animal Behaviour, 44: 207 -221.
Eluvathingal, L.M., Shanbhag, B.A. & Saidapur, S.K. (2009) Association preference and mechanism of kin recognition in tadpoles of the toad Bufo melanostictus. Journal of Bioscience, 34 (3): 435–444.
Gray, H.M., Summers, K. & Ibáñez, R.D. (2009) Kin discrimination in cannibalistic tadpoles of the Green Poison Frog, Dendrobates auratus (Anura: Dendrobatidae). Phyllomedusa, 81 (1): 41-50.
Halverson, M.A., Skelly, D.K. & Caccone, A. (2006) Kin distribution of amphibian larvae in the wild. Molecular Ecology, 15: 1139–1145.
Poelman, E.H. & Dicke, M. (2007) Offering offspring as food to cannibals: oviposition strategies of Amazonian poison frogs (Dendrobates ventrimaculatus). Evolution and Ecology, 21: 215–227.
Pizzatto, L., Stockwell, M., Clulow, S., Clulow, J. & Mahony, M. (2016) How to form a group: effects of heterospecifics, kinship and familiarity in the grouping preference of green and golden bell frog tadpoles. Journal of Herpetology, 26: 157–164.
Rajput, A.P., Saidapur, S.K. & Shanbhag, B.A. (2014) Kin discrimination in tadpoles of Hylarana
temporalis (Anura: Ranidae) and Sphaerotheca breviceps (Anura: Dicroglossidae): influence of hydroperiod and social habits. Phyllomedusa, 13 (2): 119–131.
We now enter the final month of the Scottish Dragon Finder project but activities are still occurring thick and fast! We held our final volunteer day of the project at Riverside Nature Park, Dundee which had to be delayed due to snow previously in March. Volunteers helped plant up the ponds created last winter with native plants to create what should be a superb habitat for amphibians come next spring. Many thanks to Plants for Ponds (www.plantsforponds.co.uk) for donating some fabulous species for our volunteer day!
We are re-visiting the habitat sites worked on during Scottish Dragon Finder and this is now well underway with 15 sites visited across Scotland. Staff have been checking the pond’s conditions whilst sampling for aquatic invertebrates and amphibians. It has also been a great chance to get some final footage of the amazing ponds created and restored.
Our final Dragons in your Garden session was held at the start of May in North Ayrshire with the Three Town Growers Allotments and Community Garden. Attendees learnt about wildlife gardening for reptiles and amphibians through a talk and our model wildlife garden activity. The group were also in the stages of developing their own wildlife pond so an additional talk on pond creation and management was included, followed by a visit to the location of the pond. At this time attendees could make suggestions for the new pond using knowledge shared through the workshop and it is hoped a thriving wildlife pond will be established in the months to come.
Our final survey training session took place at Calderglen Country Park in South Lanarkshire in mid- May. Attendees learnt about the native amphibians and reptiles in Scotland before visiting ponds and learning survey techniques for amphibians. Those who attended can now use these skills in the future to help find and identify amphibians and reptiles – whilst submitting their sightings through the free Dragon Finder app can directly help Froglife’s work in the future.
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