Climate change has already increased the spread and severity of a fatal disease caused by Ranavirus that infects common frogs (Rana temporaria) in the UK, according to research led by ZSL’s Institute of Zoology, UCL and Queen Mary University of London published on 10 May 2019. For full details click here.
There are currently 8,004 species of amphibian (AmphibiaWeb, 2019) of which 88%, (7,064 species) are frogs and toads (anurans). These species exhibit an astonishing range of reproductive modes, of which only a small proportion lay eggs in water which hatch into aquatic larvae. In total, anurans exhibit 40 different modes of reproduction which are based on where the eggs are laid, egg type, and patterns of larval development. Examples of different reproductive modes include: depositing eggs in foam nests which float on water; laying eggs on the back of the female; laying eggs on the ground or in burrows; and depositing eggs on leaves with tadpoles that hatch and fall into water below (Duellman & Trueb, 1986). Of the 40 modes, direct developing embryos are perhaps the most unusual for amphibians. In these species, no water is required for development and instead the tadpoles develop within eggs which then hatch directly into froglets. This type of reproduction has evolved multiple times independently in anurans and currently 1,400 species are recognised to develop in this way (Stuart et al., 2008). Our knowledge of the full range of reproductive modes is still lacking as new patterns of reproduction are still being discovered. For example, some recent discoveries include novel nest building behaviour in the Kumbara night frog (Nyctibatrachus kumbara) from southern India (Gururaja et al., 2014) and unique foot-flagging behaviour has been observed in the Wayanad dancing frog (Micrixalus saxicola) a small torrent frog from India (Preininger et al., 2013). In this article we discuss some further recent discoveries of novel reproductive behaviours in anurans.
The Western Gnats in southern India has been a recent hotspot in discoveries of novel reproductive behaviours in anurans. Due to its glacial history and diversity of habitats, this region supports over 180 species of amphibian which exhibit a range of reproductive patterns. The Chalazodes bubble nest frog (Raorchestes chalazodes) inhabits remote tropical forests in the Western Gnats. This species was presumed to be extinct, until its recent rediscovery in 2011 (Ganesan et al., 2019). Sheshadri et al. (2015), have recently reported a unique breeding behaviour in this frog. Males were found living inside the shafts of bamboo canes where they guarded the eggs laid by the females (Figure 1). It appears that small holes created by insects in the lower shafts of bamboo canes are utilised by this frog, which uses the hollow interior for breeding. Males call to attract females, which lay 5-8 large eggs in clusters inside the bamboo. The male guards these eggs from predators until they hatch into free-living froglets. This is the first time that this type of reproduction has been recorded in any amphibian species and thus represents a unique reproductive mode (Sheshadri et al., 2015). Unfortunately, this frog remains critically endangered, only occurring in five localities, and is highly threatened due to over-harvesting of bamboo (Sheshadri et al., 2015). Unless unregulated overharvest of bamboo is halted, this species may well go extinct due to lack of suitable breeding habitat.Figure 1. Left: Adult Chalazodes bubble nest frog (Raorchestes chalazodes) on top of a bamboo cane; Right: cross section of bamboo cane showing clutch of eggs and an emerging froglet.
Many species of male anuran possess vocal sacs which they use during breeding to vocalise to attract females. In several frog species visual cues of the inflating vocal sac make the acoustic signal more attractive to females or aid to deter competing males. Male African reed frogs (Hyperoliidae) possess a prominent gular patch on the vocal sac which they use to attract females and may also function as a visual cue to competing males (Figure 2). Starnberger et al. (2018) found that in the spotted reed frogs (Hyperolius puncticulatus) males do not respond to the vocal sac of other males but when they heard males calling they performed a previously undescribed gestural display: a tapping behaviour consisting of a series of front and hind limb lifts. It is thought that these gestures serve to deter males and also attract females who may be close by (Starnberger et al., 2018).F
Many anurans form amplexus during breeding where by the male takes the female in an embrace. Since fertilization is external in most anurans, the position of the male ensures that he is able to release his sperm to fertilize her eggs as she releases them. The night frogs (genus Nyctibatrachus) from India contains 28 species, many of which have only recently been described. In all Nyctibatrachus species, egg clutches are deposited on rocks or vegetation overhanging water, and tadpoles fall in the water after hatching, where they continue their development. Several novel types of amplexus have been described in this genus (reviewed in Willaert et al., 2016) such as a short axillary amplexus in pairs of the Kumbara night frog (N. kumbara) followed by a handstand, or the complete absence of amplexus in N. petraeus where the female deposits her eggs prior to the male fertilizing them. Willaert et al. (2016) have recently discovered a new breeding behaviour in the Bombay night frog (N. humayuni). During breeding the male forms a loose amplexus on the female, lasting only a few seconds and differs from all previously described amplexus types in anurans. When mounted, the male rests on the female without grabbing her tightly, but instead uses his hands to hold on to a leaf, branch or tree trunk (Willaert et al., 2016). Since the male does not have time to fertilise the eggs whilst engaged with the female, the authors propose that the male releases his sperm onto the back of the female and the eggs are subsequently fertilized by the sperm running down her back and hind legs. This hypothesis is supported by the observation that the female remains motionless after egg deposition for several minutes with her hind legs stretched around the freshly deposited clutch (Willaert et al., 2016) (Figure 3). In addition, females have been observed to make a call which is highly unusual. Female calling behaviour has so far only been reported in only 25 anurans, representing less than 0.5% of the total anuran species that are currently recognized (Willaert et al., 2016). It appears that the females call to aid in mate recognition and location.
This study, along with others recently published, demonstrate the range of reproductive behaviours that are exhibited amongst anurans. The Nyctibatrachus frogs are one of several unique taxa in the Western Ghats biodiversity hotspot and are heavily threatened by human activities. Understanding the ecology of these and other poorly known species is of major importance for planning and successfully implementing conservation strategies.
AmphibiaWeb (2019). <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Apr 2019.
Duellman, W.E. & Trueb, L. (1986) Biology of Amphibians, McGraw-Hill Publishing Company, United States of America.
Ganesan, R., Seshadri, K.S. & Biju, S.D. (2019) Lost! Amphibians of India. Available at: http://www.lostspeciesindia.org/LAI2/new1_rediscovered.php. Accessed 18 April 2019.
Gururaja, K.V., Dinesh, K.P., Priti, H. & Ravikanth, G. (2014) Mud- packing frog: a novel breeding behaviour and parental care in a stream dwelling new species of Nyctibatrachus (Amphibia, Anura, Nyctibatrachus). Zootaxa, 3796: 33-61.
Preininger, D., Boeckle, M., Freudmann, A., Starnberger, I., Sztatecsny, M. & Hödl M. (2013) Multimodal signaling in the Small Torrent Frog (Micrixalus saxicola) in a complex acoustic environment. Behavioral Ecology and Sociobiology, 67: 1449–1456.
Seshadri, K.S., Gururaja, K.V. & Bickford, D.P. (2015) Breeding in bamboo: a novel anuran reproductive strategy discovered in Rhacophorid frogs of the Western Ghats, India. Biological Journal of the Linnean Society, 14 (1): 1-11. https://doi.org/10.1111/bij.12388
Starnberger, I., Maier, P.M., Hödl, W. & Preininger, D. (2018) Multimodal signal testing reveals gestural tapping behavior in spotted reed frogs. Herpetologica, 74 (2): 127–134.
Stuart, S.N., Hoffmann, M., Chanson, J.S., Cox, N.A., Berridge, R.J., Ramani, P. & Young, B.E. (2008) Threatened Amphibians of the World. Barcelona, Spain: Lynx Edicions; Gland, Switzerland: IUCN, Arlington, Virginia, USA: Conservation International.
Willaert, B., Suyesh, R., Garg, S., Giri, V.B., Bee, M.A. & Biju, S.D. (2016) A unique mating strategy without physical contact during fertilization in Bombay Night Frogs (Nyctibatrachus humayuni) with the description of a new form of amplexus and female call. PeerJ 4:e2117; DOI 10.7717/peerj.2117
What animals are up to this month… May 2019 edition
May marks the end of the breeding period for the Common Toad. However another native toad of the UK, the Natterjack Toad, may have recently emerged from it’s overwintering state anytime from March to early May (the latter in colder climes in Scotland). Natterjack toads may breed from April – July, but mid-May can be the peak time for this activity. Male calls are very loud and can be heard up to 2km away. Their spawn is similar to the strings of eggs laid by the Common Toad wrapped around vegetation. However Natterjack Toad spawn consists of rows of singles eggs, as opposed to the Common Toad double egg strings.
Our native newt species will be in their highest numbers in ponds around this time with peak breeding activity in April and May. Males require areas of open water in a pond to display and court females which may lead to fertilisation of eggs, after which females will begin laying eggs – individually wrapped in leaves with an adhesive substance offering protection from predation and sunlight. Females may lay and wrap hundreds of eggs depending on the species and will have some busy days ahead!
Remember to record your amphibian and reptile sightings on our Dragon Finder app available to download here.
There are so many ways that you can help Froglife in their conservation efforts to protect reptiles, amphibians and their habitats.
The Froglife Shop: Do you have a person in your life who would appreciate a gift that is something a little bit different? Take a look in our Froglife shop for ideas knowing that your purchases will help our important work.
A one-off donation: If you would like to give Froglife a one-off donation, click here to donate as much or as little as you like. Every penny will help us!
Other ways to donate: There are lots of different ways that you can make a direct donation to us including corporate sponsorship or sponsoring a specific project. Take a look here.
Froglife Friendship: Froglife Friendship costs from as little as £1.50 a month. As well as knowing your contribution is going toward the conservation of the UK’s amphibians and reptiles you’ll also receive regular updates from us and special offers. Click here for more information.
Fundraise for us: Thinking of fundraising for us? It can be anything from a sponsored swim/walk to a bake sale. Take a look here to see the many different ways you can fundraise for Froglife.
Legacies: Leaving a legacy to charity is an incredibly valuable way to make a lasting difference to a cause you love and support. To find out more about how you can leave a legacy to Froglife in your will, click here
CollecTins: Keep an eye out at our events for our ‘CollecTins’ you can donate to us with a simple contactless payment (£10 is just an example, other amounts are available)
Scotland supports six species of native amphibian and four native reptile species. These charismatic species form a valuable part of Scotland’s biodiversity and form an important role in effective ecosystem functioning. Most are secretive and often go unnoticed, but are appreciated in the many and diverse habitats where they occur. Common frogs and common toads are perhaps the most well recorded species, being obvious in parks and gardens during spring breeding and migration (Figure 1). Both species have a widespread distribution along with smooth newts and palmate newts which are more secretive. Great crested newts have a more scattered distribution in Scotland while the nattterjack toad is confined to a small number of isolated saltmarshes along the Solway coast. In addition one introduced species, the alpine newt, occurs at a few sites across central Scotland. The three established native reptiles in Scotland include the adder (or northern viper), slow-worm and common lizard. Adders may be seen basking in warm sunshine in March and slow-worms often frequent garden or allotment compost heaps. In addition, the grass snake has recently been reported as occurring in the southern belt, particularly around Dumfries and Galloway (McInerny & Minting, 2016). Around the inshore waters a number of turtle species have been recorded including the leatherback turtle, loggerhead turtle and Kemp’s ridley sea turtle.
In recent decades populations of our most common amphibian and reptile species are under threat from a number of anthropogenic factors including habitat loss and fragmentation, introduced diseases, pollution and climate change (Downie et al., in press) (Figure 2). The Fight for Scotland’s Nature campaign (www.fightforscotlandsnature.scot) aims to raise awareness of the plight of Scotland’s valuable species and protect and enhance Scotland’s natural environment. If you would like to help, please sign the petition/respond to the consultation at www.fightforscotlandsnature.scot/action/.
One of the biggest factors contributing to declines in Scotland’s native amphibian and reptile populations is habitat loss. For amphibians pond loss, coupled with a reduction in terrestrial habitat, has resulted in declines in many species. Research carried out by Froglife in 2016 showed that across the UK, common toad populations have declined by 68% over the past 30 years (Petrovan & Schmidt, 2016). In addition, filling in of garden ponds is likely to have negatively impacted common frog populations, which thrive in urban habitats and rely on garden features such as ponds for their successful breeding. Habitat fragmentation is also a big problem, especially for migratory species with habitual breeding ponds such as common toads and great crested newts. Collisions of amphibians on roads can lead to massive mortality and is one of the factors thought to be responsible for the long-term decline in UK and continental European toad populations (Petrovan & Schmidt, 2016) (Figure 3). Introduced diseases including Ranavirus have had negative impacts on common frog populations. Also, a rise in the pet trade and an increase in members of the public housing exotic pets, has increased the risk that emerging infectious diseases like Batrachochytrium salamandrivorans (Bsal) will become introduced into wild newt populations (Cunningham et al., 2019).
In an attempt to combat these threats, the national charity Froglife are carrying out a number of conservation programmes to help a range of amphibian and reptile species. The Come Forth for Wildlife project is in its development phase, thanks to funding from the National Lottery Heritage Fund. If the main project is funded, this will tackle habitat loss in the Forth region of southern Scotland. Through targeted restoration and creation of amphibian and reptile habitats, along with public education programmes, we will help preserve vital habitats for these species in this highly populated region of Scotland. Once habitats have been created and restored, Froglife are committed to re-visiting each site 1, 3, 5 and 10 years post-completion to ensure that they remain viable and successful for maintaining amphibian and reptile populations.
Road mitigation schemes are increasingly using under-road tunnels or culverts to help direct movements of amphibians from terrestrial to breeding habitats and prevent the negative effects of habitat fragmentation. Little research has demonstrated the success of tunnels in providing suitable corridors for amphibians. Research by Froglife in England has suggested that in certain circumstances tunnels may be effective in mitigating the impacts of road construction by linking key habitats, especially for the protected great crested newt (Jarvis et al., 2019). However, no research has demonstrated the success of tunnels for great crested newts in Scotland, where this species may have different habitat requirements (Harper et al., 2019). Froglife is carrying out a study on six newly created amphibian mitigation road tunnels at a site in southern Scotland with nationally significant populations of great crested newts. The research will determine whether the implementation of tunnels at this site is successful and will be important for determining the success of future tunnel mitigation projects.
Amphibians and reptiles face an uncertain future in Scotland but you can help by supporting The Fight for Scotland’s Nature campaign (www.fightforscotlandsnature.scot). This will help us to work together to protect the valuable amphibian and reptile species of Scotland, enable us to set clear ambitions for Scotland’s environmental policy, conserve habitats and create a more sustainable future.
Cunningham, A. A., Smith, F., McKinley, T. J., Perkins, M. W., Fitzpatrick, L. D., Wright, O. N. & Lawson, B. (2019) Apparent absence of Batrachochytrium salamandrivorans in wild urodeles in the United Kingdom. Nature Scientific Reports, 9: 2831. https://doi.org/10.1038/s41598-019-39338.
Downie, J. R., Larcombe, V. & Stead, J. (in press) Amphibian conservation in Scotland: a review of threats and opportunities. Aquatic Conservation: Marine and Freshwater Ecosystems.
Harper, L. R., Downie, R., McNeill, D. C. (2019) Assessment of habitat and survey criteria for the great crested newt (Triturus cristatus) in Scotland: a case study on a translocated population. Hydrobiologia, 828: 57–71. https://doi.org/10.1007/s10750-018-3796-4.
Jarvis, L. E., Hartup, M. & Petrovan, S. O. (2019) Road mitigation using tunnels and fences promotes site connectivity and population expansion for a protected amphibian. European Journal of Wildlife Research, 65: 27-38. https://doi.org/10.1007/s10344-019-1263-9.
McInerny, C. J. & Minting, P. (2016) The Amphibians and Reptiles of Scotland. Glasgow, Glasgow Natural History Society.
Petrovan, S. P. & Schmidt, B. R. (2016) Volunteer conservation action data reveals large-scale and long-term negative population trends of a widespread amphibian, the common toad (Bufo bufo). PLoS ONE, 11 (10): e0161943. https://doi.org/10.1371/journal.pone.0161943.
TOAD PATROLLERS There is a tadpole phenomenon that appears in North America, but we are trying to find out if it occurs in the UK. Take a look here. Do you know of a large, open-water pond with little vegetation where huge shoals of tadpoles display this behaviour?
Please get in touch with Laurence.email@example.com