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What our animals are doing this month… January 2020

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It’s a new year for amphibians and reptiles! Whilst you might not think our species are very active at this time of the year one species may been seen laying eggs by the end of this month…

Our common frog breeds from their 2nd or 3rd year, often returning to the ponds from which they originally spawned.  Male frogs attract female frogs by ‘croaking’ – this is a soft repetitive sound which also serves to intimidate other males. 

Frogspawn might be seen from January onwards into March, with the first sightings of frogspawn often in the south-west of the UK.  The effects of unpredictable weather conditions can make it difficult for breeding common frog who use the temperature as a cue.  As we have the potential to experience mild winters this can be confusing.  These out of season warmer temperatures have even resulted in frogspawn sightings in October / November in the past!  Studies suggest that common frog spawning is becoming earlier – with research showing a 10C rise in temperature equating to a 5.1 day advance in frogspawn arrival (Carroll et al. 2009).

Frogspawn won’t survive freezing should colder temperatures return after a mild spell – however spawn under the surface of the water would likely survive if freezing does not persist in the long term.

You can help by submitting your sightings of frogspawn and any other amphibians and reptiles with our Dragon Finder App (https://www.froglife.org/dragonfinder/app/) – these records help us learn more about how our changing environment affects our species.

Common frog breed the earliest of our native amphibian species – with early sightings of frogspawn possible in January!

Croaking Science- Foot flagging: an alternative method of communication in frogs

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Traditionally, frogs and toads are considered to communicate primarily by using acoustic cues, with males typically calling to attract females. However, in noisy tropical rainforests by fast flowing streams, acoustic communication becomes more problematic. In these environments male frogs have evolved an array of visual cues which complement acoustic cues to communicate between each other and to also attract females. Visual communication has evolved independently in several lineages of frog species, mainly in diurnal species inhabiting noisy, stream-side environments.

Figure 1. Male frogs using foot-flagging in male-male communication. [Photo credit: Amézquita & Hödl, 2004.]

Foot-flagging has been observed in 16 frog species (Preininger et al., 2013). The male will typically arch and rotate its back foot in the air, giving a conspicuous visual signal (Figure 1). Males of the Bornean frog genus Staurois have evolved a unique foot-flagging behaviour which males use in a variety of contexts. The Sabah splash frog (Staurois latopalmatus) is found exclusively close to waterfalls where it can be observed regularly on exposed perches. Within this habitat, males signal in close vicinity to each other near to the water (Preininger et al., 2009). Preininger et al. (2009) have identified three types of visual displays: foot flagging, arm waving and vocal sac displays. Foot-flagging displays are mainly performed in the direction of a male opponent and appear to be used in territorial defence. Preininger et al. (2009) hypothesise that foot-flagging behaviour in this species has evolved from physical male-male combat where each male tries to push the other off its perch. The foot-flagging behaviour may be a ritualization of this aggressive combat, avoiding the need for physical contact. The other visual displays, arm waving and throat display appear to be used less frequently than foot-flagging during male-male aggressive encounters.

Figure 2. The Bornean rock frog (Staurois parvus) (left) from Borneo and the small torrent frog (Micrixalus saxicola) (right) from the Western Ghats of India both exhibit foot-flagging behaviour. [Photo credits: (left) Mohamad Jakaria, https://commons.wikimedia.org/wiki/File:Staurois_parvus.jpg; (right) L. Shyamal, https://commons.wikimedia.org/wiki/File:MicrixalusSaxicola1.jpg]

The Bornean rock frog (Staurois parvus) from Borneo and the small torrent frog (Micrixalus saxicola) from the Western Ghats of India belong to different frog families (Figure 2). Males of both species use complex signalling involving high pitched calls, foot flagging, and tapping (foot lifting) to defend perching sites against other males (Preininger et al. 2013). The Bornean rock frog has conspicuous white feet, whereas the small torrent frog has feet which are the same colour as its body. In a study to examine the differences in the behaviour of the two species, Preininger et al. (2013) found that in the Bornean rock frog, foot-flagging achieved a 13 times higher contrast against their visual background than the feet of the small torrent frog. In addition, the Bornean rock frog primarily responded to stimuli with foot flagging, whereas the small torrent frog responded mainly with calls but never foot-flagging on its own (Preininger et al. 2013). The authors propose that in the small torrent frog foot-flagging is in a transient state, evolving from its current use in physical fighting behaviour.

The colouration on the feet of foot-flagging species may signal more than male presence. Research by Stangel et al. (2015) has found that in two species (Staurois parvus and S. guttatus) the brightness of the feet increases with age. The peak brightness seems to coincide with sexual maturity and may be linked to androgen hormone levels in the males. The foot-flagging in these species may therefore convey information on the status of the male and his receptiveness to mate. This may be useful both to intruding males and also females which may be in the area.

African puddle frogs of the genus Phrynobatrachus are unique to Africa and are named after their breeding strategy of often laying large numbers of eggs in slow-moving or stagnant water bodies. In East African mountain streams lives a day time active frog, krefft’s river frog (Phrynobatrachus krefftii). Like other members of its genus males are dull brown in colour but also possess a striking bright yellow vocal sac (Figure 3). Instead of using foot-flagging for visual communication, males of this species communicate using a combination of acoustic cues and exhibiting their bright yellow vocal sac. Sometimes males will utter a call, accompanied by exhibiting their yellow vocal sac, whereas at other times no call will be emitted. Hirschmann & Hödl (2006) propose that the use of their brightly coloured vocal sac in this way has evolved to indicate the aggressive motivational state in the male.

Figure 3. Male krefft’s river frog (Phrynobatrachus krefftii) (right) possess a bright yellow vocal which they use in visual communication. Females (left) lack this colouration. [Photo credit: Hirschmann & Hödl, 2006.]

Further research into foot-flagging and other visual displays at different life stages will help increase our understanding of the function, development and evolution of visual signals in amphibians. Foot-flagging is only confined to a relatively few number of frog species and these are unable to survive in habitats modified for human use. Habitats where many of these unique species occur are increasingly threatened with habitat loss and fragmentation. Understanding the ecology of these species is therefore crucial in identifying and protecting key habitats in the wild.

References

Amézquita, A. & Hödl, W. (2004) How, when and where to perform visual displays: the case of the Amazonian frog Hyla parviceps. Herpetologica, 60 (4): 420–429.

Hirschmann, W. & Hödl, W. (2006) Visual signaling in Phrynobatrachus krefftii Boulenger, 1909 (Anura: Ranidae). Herpetologica, 62 (1): 18–27.

Preininger, D., Boechle, M. & Hödl, W. (2009) Communication in noisy environments II: visual signaling behavior of male foot-flagging frogs Staurois latopalmatus. Herpetologica, 65 (2): 166–173.

Preininger, D., Boechle, M., Sztatecsny, M. & Hödl, W. (2013) Divergent receiver responses to components of multimodal signals in two foot-flagging frog species. PLoS ONE, 8 (1): e55367. doi:10.1371/journal.pone.0055367.

Stangel, J., Preininger, D., Sztatecsny, M. & Hödl, W. (2015) Ontogenetic change of signal brightness in the foot-flagging frog species Staurois parvus and Staurois guttatus. Herpetologica, 71 (1): 1–7.

West Yorkshire Toad Summit 2020

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toads on roads logoFroglife’s annual Toad Summit returns, this year taking place in Halifax, West Yorkshire. Our partners are Calderdale Council, Halifax Scientific Society, Amphibian and Reptile Groups UK (ARG-UK) and local toad patrols. It is an excellent opportunity for Toad Patrol members and fellow toad enthusiasts to get together, share ideas, and learn more about the best ways to conserve our native toads.

The afternoon will include a short programme of talks with plenty of time for discussion and networking.

Speakers include:

Angela Julian, Amphibians and Reptile groups UK

Gordon Maclellan, Creeping Toad

Hugh Firman, Calderdale Council

Steve Blacksmith, Halifax Scientific Society

Local Toad Patrol Managers

This event is FREE and takes place on Saturday 25th January 2020. The event is open to all Toad Patrollers and anyone else interested in learning more about toad conservation. For further information and to register for your free ticket, click here. 

Croaking Science: Artificial light at night- a problem for amphibians?

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Light pollution from industrialization, urban and suburban development is spreading rapidly across the world. It is estimated that 20% of land on earth is polluted by artificial light (Cinzano et al., 2001). An increasing range of wild animal species are being exposed to levels of night-time light higher than ever before. It is estimated that the average amount of light reaching the ground from one street lamp is 50 lux, compared to 0.1 lux of bright moonlight (Bennie et al., 2016) (Figure 1). Car headlights may reach over 1,000 lux, some 10,000 higher than natural night time light exposure. These levels of artificial light have been shown to affect a range of animal taxa from mammals to birds, reptiles and insects. The impacts of artificial light on amphibians appear to be varied, depending on the species and their ecology (reviewed in Dutta, 2018). For example, the calling behaviour of many frog species appears to be affected, with individuals calling less frequently and moving more often. This has the potential for decreasing mating opportunities and negatively impacting on subsequent spawning success. However, certain species, such as the cane toad (Bufo marinus) appear to benefit from street lights, foraging more often on the insects which congregate beneath them at night. On the contrary, red-backed salamanders (Plethodon cinereus) from North America forage less under artificial light, hiding in the leaf litter. This may have consequences on an individual’s ability to effectively forage and feed at night. Road mortality may be increased in areas of artificial light as has been shown in the American toad (Bufo americanus), which is attracted to street lighting and is more likely to cross roads (Mazerolle, 2004). Indirect effects of artificial light may include increased detection by predators and subsequent mortality of amphibians.

Figure 1. The amount of light generated by one street light can be several hundred or even several thousand times brighter than moonlight.
[Photo credit: Hackspett1265, https://commons.wikimedia.org/wiki/File:Night_light_behind_tree.jpg]

Artificial light may impact a range of amphibian life stages including the growth, development and activity of larvae, juveniles and adults. Our understanding of how artificial light may impact each life-stage is not fully understood. Dananay & Benard (2018) carried out experiments to determine the impacts of artificial light on larval and juvenile American toads. The researchers did not find any significant impact of artificial light on larval growth or behaviour, but juvenile American toads were affected. Juvenile toads under artificial light treatment were more active than those under dark treatments and had growth rates 15% lower than those in dark treatments. This increased nocturnal activity by juveniles under artificial light conditions appears to have resulted in increased energy expenditure and thus reduced growth rates (Dananay & Benard, 2018). This reduced growth may result in delayed reproductive maturity, lower fertility and reduced survival. Combined with other stressors, such as climate change, this could lead to population declines in many of our common amphibian species.

Figure 2. Juvenile toads under artificial light at night experienced lower growth rates which may result in delayed reproductive maturity, lower fertility and reduced survival (Dananay & Benard, 2018).
[Photo credit: Fungus Guy, https://commons.wikimedia.org/wiki/File:Eastern_American_toad_(Sudden_Tract).jpg]

Habitats restored for recreational purposes, as well as for wildlife, including amphibians, are often situated close to towns and cities. The light intensity reaching wetland areas close to cities may be greater than the brightest full moon (Secondi et al., 2017). Common toads (Bufo bufo), may be particularly affected by increased levels of artificial light as they have a very short breeding season and may use light to orient towards ponds and aid in synchronicity in breeding. Touzet et al. (2019) carried out research on the common toad in France to examine toad behaviour under artificial light generated by street and outdoor lighting in semi-urban areas. After 20 days of nocturnal exposure during the breeding period at 5 lux the total time spent active by male common toads decreased by more than half; at 20 lux activity levels dropped by 73%. This was due to male toads being less active during nocturnal periods (Touzet et al., 2019). In addition, common toads decreased their active energy expenditure by 18% at 5 lux and 38% at 20 lux, probably due to increased stress (Touzet et al., 2019). The authors conclude that the alteration of both activity and energy metabolism could have negative impacts on common toad reproduction and ultimately lead to a reduction in survival.

The impacts of artificial light on amphibians may not always be negative and some species seem to be resistant to anthropogenic light sources at night. Underhill & Höbel (2018) tested the effects of artificial light on the breeding behaviour of female eastern gray treefrogs (Hyla versicolor). Contrary to expectation, the researchers found no effects of artificial light on mating preferences and breeding behaviour. In this species, increased levels of artificial light should not affect population persistence nor affect mate choice. This is in contrast to túngara frogs (Engystomops pustulosus) which changed their behaviour under different light conditions in a way that suggested that they felt safer under darker conditions (Rand et al., 1997). Frog species vary in their sensitivity to light and the degree that they use visual cues for orientation and reproduction. The eastern gray treefrog does not rely heavily on visual cues for mate selection which may explain the lack of significant impacts of artificial light on their breeding behaviour (Underhill & Höbel, 2018).

Figure 3. The eastern gray treefrog (Hyla versicolor) from North America appears resistant to the effects of artificial light.
[Photo credit: Cliff, https://commons.wikimedia.org/wiki/File:Grey_Tree_Frog_(Hyla_versicolor)_(3151990943).jpg]

It appears that there is no consistent and universal impact of artificial light on amphibians. The response seems to vary by species depending on their ecology and breeding biology and their reliance on visual cues. In addition, responses by individual populations are likely to vary depending on location and the amount of artificial light. However, in many cases it appears that artificial light may have negative impacts on amphibian populations. Further research is required at a population level to determine the long-term impacts of artificial light and possible synergistic interactions with other environmental stresses such as habitat loss, fragmentation, pollutants and climate change.

References

Bennie, J., Davies, T.W., Cruse, D. & Gaston, K.J. (2016) Ecological effects of artificial light at night on wild plants. Journal of Ecology, 104: 611–620.

Cinzano, P., Falchi, F., & Elvidge, C.D. (2001) The first world atlas of the artificial night sky brightness. Monthly Notices of the Royal Astronomical Society, 328: 689–707. https://doi.org/10.1046/j.1365-8711.2001.04882.x

Dananay, K.L. & Benard, M.F. (2018) Artificial light at night decreases metamorphic duration and juvenile growth in a widespread amphibian. Proceedings of the Royal Society, London B, 285:

20180367. http://dx.doi.org/10.1098/rspb.2018.0367.

Dutta, H. (2018) Insights into the impacts of three current environmental problems on Amphibians. European Journal of Ecology, 4 (2): 15-27, doi:10.2478/eje-2018-0009

Feuka, A.B., Hoffmann, K.E., Hunter Jr, M.L. & Calhoun, A.J.K. (2017) Effects of light pollution on habitat selection in post-metamorphic wood frogs (Rana sylvaticus) and unisexual blue-spotted salamanders (Ambystoma laterale × jeffersonianum). Herpetological Conservation and Biology, 12 (2):470–476

Mazerolle, M.J. (2004) Amphibian road mortality in response to nightly variations in traffic intensity. Herpetologica, 60 (1): 45-53.

Rand, A. S., Bridarolli, M. E., Dries, L., & Ryan, M. J. (1997). Light levels influence female choice in túngara frogs: Predation risk assessment? Copeia, 1997, 447–450. https://doi.org/10.2307/1447770.

Secondi, J., Dupont, V., Davranche, A., Mondy, N., Lengagne, T. & Théry, M. (2017) Variability of surface and underwater nocturnal spectral irradiance with the presence of clouds in urban and peri-urban wetlands. PLoS One, 12: e0186808. doi:10.1371/journal.pone.0186808.

Touzot, M., Teulier, L., Langagne, T., Secondi, J., Théry, M., Libourel, P., Guillard, L. & Mondy, N. (2019) Artificial light at night disturbs the activity and energy allocation of the common toad during the breeding period. Conservation Physiology, 7 (1): coz002; doi:10.1093/conphys/coz002

Underhill, V.A. & Höbel, G. (2018) Mate choice behavior of female Eastern Gray Treefrogs (Hyla versicolor) is robust to anthropogenic light pollution. Ethology, 124: 537–548. doi:10.1111/eth.12759

What our animals are doing this month… December 2019

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It’s the final month of the year with activity in our ponds significantly decreased with the cold weather.  However our frogs may still be in the pond over the winter.  Male common frog in particular are known for overwintering at the bottom of ponds within the silt at which time they shut down and absorb oxygen from the water.  If these oxygen levels in the pond become low in freezing temperatures you may see frogs swimming around the pond searching out oxygen supplies.  Native plants in the pond will photosynthesize and produce oxygen, which is very helpful for overwintering frogs, as long as the plants are receiving sunlight.  Carefully clearing snow from a snowed over pond can help this sunlight reach the plants.

Adders are known for being a hardy species in the cold weather and may become active over winter if we have quite mild winter conditions.  There are sightings for every month of the year for adders as they may take advantage of the chance to bask in the sunlight.  This likely impact of climate change however may not be beneficial for the species.  Leaving overwintering sites on milder days can cause the animal to be susceptible to sudden cold snaps in addition to their potential loss of stored energy by being active without the option of foraging for new energy sources.

This frozen pond could be the wintery home for a common frog!  Keeping it clear of snow with plants in the pond will help oxygen levels.

Object to Development at Stewartfield Heritage Loch

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Froglife’s Toads on Roads project has been running for many, many years and, thanks to the hard work of toad patrollers, thousands of toads are rescued every year. However, common toads are under threat. One of the main reasons being more deaths on roads due to traffic values increasing and more and more roads being constructed on valuable toad habitat. 

Stewartfield Heritage Loch, one of the many valued Toads on Roads crossing sites, is under threat due to an application to build a dual carriageway. Situated on the edge of a built-up area, Stewartfield Heritage Park provides a crucial habitat for common toads. It features the 16-acre loch and excellent surrounding habitat as well as supporting a nature reserve with a large pond where toads are able to breed. Many of the toads who depend on the park for their survival migrate to wider habitats on the opposite side of the busy Stewartfield Way. Toads already face danger when crossing this road, the dualling of this would make it almost impossible for them to cross without being killed and would significantly encroach into their essential habitat.

The crossing manager really needs your help to object to the construction. Please click this link and remember to include the points below in your objection. (see Froglife’s objection letter here) The closing date for this is 20th December:

  1. The toads will be killed when crossing the road en-masse during their spring migration to breed (which is essential for survival of the population) and when migrating to wider habitats, including gardens on the other side of the road. Baby toads will be killed as they emerge from the pond en-masse in summer.
  2. The widening of the road will bring it directly adjacent to the breeding pond, removing the current screening, and will destroy a large amount of the habitat toads require for refuge, foraging and hibernation. During the construction phase of the road, the habitat where the toads live and need to cross will be totally unviable, and many will undoubtedly be killed.
  3. Toad populations have declined by 68% in the last 30 years. A large cause of this is deaths on roads and loss of habitat. This development would seriously threaten this crucial toad population. It is essential to protect our common toads for future generations. 

Pictured: the breeding pond and one of the many toads that use it 

Pictured: The loch