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WILDLIFE IN BRITIS COLUMBIAAT RISK
Oregon Spotted Frog
This endangered amphibian is at risk due to loss of shallow wetland habitat to agriculture and development.
Ministry of Water, Land and Air Protection Besides directly reducing the diseases as iridoviruses and chytrid amount of available wetland habitat, fungi. urbanization has also affected the Because of their permeable skin, all Oregon Spotted Frog indirectly by amphibians are very vulnerable to Why are Oregon Spotted covering large areas with impervious water-carried pollutants. The proxim- Frogs at risk? surfaces, such as asphalt, rooftops ity of surviving Oregon Spotted Frog abitat loss is the number one reason and compacted soil. This alters both populations to agricultural areas puts for the dramatic decline of the groundwater storage and surface them at high risk from agricultural Oregon Spotted Frog throughout its run-off. The margins of the shallow chemicals that get washed into wet- HNorth American range over the past wetlands used by the Oregon Spotted lands, especially nitrogen-based com- century. There are, however, several Frog for breeding are especially sus- pounds found in crop fertilizers. A other compounding factors, all of them ceptible to hydrological changes. recent study of five Pacific Northwest the result of human activity. The Oregon Non-native invasive species, such amphibians showed that the Oregon Spotted Frog is a warm-water marsh as reed canarygrass and Bullfrogs, are Spotted Frog was the most sensitive to specialist that lives in shallow wetlands other risk factors. Reed canarygrass, environmental levels of nitrates and with emergent vegetation. This type of for example, degrades or eliminates nitrites. Levels that government agen- habitat once occurred extensively potential breeding habitat in the cies consider safe for human drink- throughout the Lower Fraser Valley and Fraser Valley and elsewhere, by form- ing water severely affected Oregon other parts of the species’ range, but it ing dense rooting mats along the Spotted Frog tadpoles. has been largely converted to other uses. shoreline that make it impassable to Over the past century, most of these Oregon Spotted Frogs. What is their status? wetlands have been drained, ditched, The non-native Bullfrog and Green istorically, the distribution of diked and filled to create additional Frog may also present serious threats. the Oregon Spotted Frog extended space for raising livestock and crops, Bullfrog populations are expanding from the extreme southwest corner establishing homes and businesses, and rapidly and the adults prey on almost Hof British Columbia to the northeast building roads. Sumas Lake, once a mas- any moving object that will fit in corner of California. Today, it has sive complex of marsh and shallow, open their mouths, including other frogs. disappeared from more than 90 percent water that spread across the Fraser Valley, Bullfrog tadpoles might also be dis- of its probable former range. Of the 63 was converted to agricultural land in the placing Oregon Spotted Frog tadpoles historical populations, only 13 remain – early 1900s. The Fraser River, which his- from the warmer, shallower waters that one in Washington State and 12 in torically flooded its banks and replenished provide optimal conditions for growth Oregon. Recent discoveries of several the valley’s wetlands each spring, has long and development. previously unknown populations – since been confined within its dikes. Natural predators, such as garter three in British Columbia, three in The few remaining patches of suit- snakes, Great Blue Herons, Raccoons Washington and 12 in Oregon – bring able Oregon Spotted Frog habitat in and Belted Kingfishers, regularly feed the number of currently known existing the Lower Fraser Valley are fragmented on Oregon Spotted Frog tadpoles, juve- populations to 31. The species is extir- and small. The three known niles and adults. pated from California. Oregon Spotted Frog popula- The Oregon Although these The three historic Oregon Spotted tions are isolated from each species normally Frog populations in British Columbia other, with no connecting cor- Spotted Frog would not exert were all located in the Fraser River ridors of habitat to allow move- has disappeared enough preda- Lowlands – on remnant wetlands in ment of individuals between tion pressure to the Sumas Prairie area, on Nicomen these areas. Biologists estimate from more be of concern, Island and in an area now encom- that the minimum habitat size than percent when prey pop- passed by Campbell Valley Regional for a viable population is at least ulations are low Park in Langley. The first two popula- two hectares and that popula- of its former their effects may tions were recorded prior to the 1950s, tions occupying habitats of less range. be significant. while the third was the subject of than 25 ha are at risk. British Oregon Spot- intensive study in the late 1960s. By the Columbia’s three populations presently ted Frogs may also be susceptible 1990s, Oregon Spotted Frogs could occupy areas of less than 13 ha. to such newly discovered amphibian not be found at any of these sites. In 1996 and 1997, a also appear on the white survey of 94 potential throat and underbelly. sites in the Lower Fraser In addition to their Valley turned up three distinctive markings, previously unrecorded they also have several Oregon Spotted Frog identifying characteris- populations, two near tics that are associated Agassiz and one near with their highly aquat- Aldergrove. The estimated ic lifestyle. One is the total of approximately The Red-legged Frog (left) has a more upright posture, longer back legs, and more full webbing between 300 frogs that inhabit pronounced dorsolateral folds than the Oregon Spotted Frog (right). The Red-legged the toes of the hind feet, Frog also has a more pronounced mask, and flecks rather than spots on its back. these three sites repre- which enhances their sent British Columbia’s, swimming ability. The and Canada’s, entire breeding popula- List along with other wildlife being other is the species’ upward-turned tion of Oregon Spotted Frogs. considered for legal designation as eyes. By having eyes that are angled Acknowledgement of the Oregon Endangered or Threatened. In Oregon upward, instead of outward like the Spotted Frog’s precarious situation it has been named as a Sensitive eyes of many other frogs, the Oregon came belatedly and only after it was Critical species and in Washington Spotted Frog is able to keep a line of proven to be a unique species, distinct State it is listed as Endangered. The sight above water, even when its head from the more widely distributed U.S. Fish and Wildlife Service has listed is almost entirely submerged. species now called the Columbia Spot- it as a Candidate species for designa- The adult Oregon Spotted Frog can ted Frog. The two species, once collec- tion under the Federal Endangered grow to a length of 44 to 100 millime- tively known as the Spotted Frog, are Species Act. tres from snout to rump, although remarkably similar in appearance. those found in British Columbia sel- Nevertheless, genetic analysis has What do they look like? dom exceed 70 mm. Females are typi- shown them to be significantly differ- he Oregon Spotted Frog (Rana pre- cally larger than males. Compared to ent and on that basis they were given tiosa) is named for the black blotches other frogs, the Oregon Spotted Frog their current names in 1997. with light centres that are scattered has relatively short legs. When sitting, In November 1999, the Oregon Tacross the back and head of adult it maintains a low,“crouching” position, Spotted Frog became the first species frogs. As a frog grows older, these spots rather than a more upright posture. to receive an emergency listing by expand in size and become ragged-look- Juveniles are light brown or olive- the Committee on the Status of ing around the edges. The spots stand green above, and white or cream Endangered Wildlife in Canada out against a back- below, with the reddish colouring of (), which declared it to In , ground body tint the underlegs and abdomen develop- be Endangered. Designations the Oregon of brown or red- ing as the frog matures. Belly mottling are normally made during dish brown, which also develops with age and is absent ’ annual species status Spotted Frog becomes increas- in newly metamorphosed frogs. review in late spring, but this became the ingly ruddy with The Red-legged Frog (Rana aurora) takes place after the Oregon age. A pair of par- has a more upright posture, and Spotted Frog’s breeding season. first species allel, light brown although it also has red legs, the red In order to give the newly to receive an to orange ridges pigment appears to be deep beneath formed Oregon Spotted Frog (called dorsolateral the surface of the skin, rather than Recovery Team a mandate to emergency folds), run part appearing “painted on” like the begin work prior to the 2000 listing by way down the Oregon Spotted Frog. breeding season, the British back, starting just Oregon Spotted Frog tadpoles are Columbia Ministry of Environ- . behind the eyes. difficult to distinguish from the ment, Lands and Parks request- The adult frog’s tadpoles of other species. Dark on ed this emergency listing. thighs and abdomen are washed with top, they have an aluminum-white In British Columbia, the Oregon orange-red pigments and are mottled or slate-coloured underbelly. As Spotted Frog is on the provincial Red with brown, grey or tan spots, which the tadpole matures, metallic flecks appear in clusters on the head, body hollow notes carry only 20 to 30 metres between risk and advantage. The and tail. However, colouring is not a and are easily obscured by birdsong risks are predation, desiccation and reliable way to identify the tadpoles or the trilling of the more vociferous freezing. The frogs do not provide of this species. Biologists rely instead Pacific Treefrog. The Oregon Spotted parental care for their eggs, so avoid- on careful measurements of tail and Frog’s mating call consists of a series of ing predation is simply a matter of body length, since they know that five to 50 “clucks” that sound like luck. Desiccation, Oregon Spotted Frog tadpoles have knocking on a log, or someone Each female’s which is fatal to proportionally longer tails than other softly clicking their tongue on egg mass is the eggs, can re- species that may be found in the the roof of their mouth. Calling sult from only a same pools. continues both night and day, deposited in small drop in the increasing in intensity on sunny a communal water level, but What makes them unique? afternoons. this risk is mini- or years, the Oregon Spotted Frog The calling males cluster in egg-laying mized as long as was lumped together with the shallow water along the edge of site. spring rainfalls Columbia Spotted Frog (Rana the breeding pond, often sit- are normal and Fluteiventris) and thought to be a sin- ting only a few centimetres apart natural run-off is unimpeded. Freez- gle species. Experienced herpetologists from each other. Females approach ing means death for exposed eggs, now tell the two apart by the amount of the group when they are ready to lay but sub-zero temperatures do not mottling on the belly, and geneticists their eggs. When a male encounters a typically occur at this time of year. differentiate them through protein receptive female he clutches her from Developing embryos can survive analysis, but it is this species’ ecological behind with his forelegs in a tight temperatures as low as 1˚C for at uniqueness that is easiest to observe and embrace called amplexus, and fertil- least eight hours, which is usually understand. izes the eggs as she lays them. Each sufficient hardiness for this region. Oregon Spotted Frogs in British female’s egg mass is deposited in a The advantage of the shallow Columbia are at the northern communal egg- sites is a warm-water environment limit of this species’ range. The few laying site, clus- that speeds embryonic development. These individuals are adapted tered with 10 to living in climatic conditions remaining to 75 other egg Present distribution that can be more extreme than masses, some of of Oregon Spotted Frog patches of Historic distribution those experienced by individu- which may end of Oregon Spotted Frog als in low-lying regions at the suitable up piled on top centre of the range. Different habitat are of others. The populations may have subtle egg-laying sites differences in their genetic fragmented are areas of still coding that reflect these adap- and small. or slow-moving tations. Biologists believe that water, usually less unique populations at the edge of a than 10 cm deep, where shoreline species’ range, such as the BC popu- vegetation is sparse. Egg masses are lations of Oregon Spotted Frog, may not attached to plants or other hold the key to species survival in the objects. face of large-scale environmental After laying her eggs, the female changes, such as global warming. goes back to leading a fairly solitary life until the next spring. The males How do they reproduce? remain together at the breeding site he Oregon Spotted Frog’s reproduc- until the end of the month-long tive cycle begins in late February or breeding season and then disperse to early March, when males move to other areas of the wetland. Ttraditional breeding sites and begin The shallow egg-laying sites calling. Theirs is no high-volume chosen by the Oregon Spotted Frog chorus. In fact, the faint, low-pitched, represent a delicate compromise The higher the water temperature sites are located in ankle-deep water (up to the maximum tolerance limit along the shoreline, where vegetation of 28˚C), the faster the embryos will is low or sparse. Adequate water levels develop into free-swimming larvae. – with no sudden flooding and, Shallow water at the edge of a pond especially, no rapid drying – are is consistently warmer than deeper critical for egg and tadpole survival. water farther out, except when temp- Deep pools are important for juve- eratures drop down near freezing. niles and adults during the dry sea- As well, in such shallow water, a great son. Mats of floating plants within amount of the jelly that surrounds these pools are used as basking the eggs is exposed to sunlight and . platforms in summer and provide Russ Haycock photo considerable heat is accumulated by cover to avoid predators. Wetlands the egg mass, so that it may be much with only their eyes protruding above with abundant aquatic and emer- warmer than the surrounding air the surface, or crouch on the muddy gent vegetation also support a rich temperature.Clustering the egg masses shoreline, waiting for prey to ap- community of invertebrates, which in one place also helps raise egg proach. As soon as the prey provide a ready temperatures by reducing the flow moves within range, the frog source of food of water around and through the lunges forward, thrusting out its Preferred for these frogs. masses. sticky tongue to trap its victim. habitat is To date, there Depending on the water tempera- Then, just as quickly, the frog is little informa- ture, the eggs hatch in 18 to 30 days. flicks its tongue back into its warm, very tion on hiber- After 13 to 16 weeks, the tadpoles mouth and swallows its meal. shallow water nation sites, but metamorphose into miniature frogs, some Oregon about half the size of full-grown Where do they live? with both Spotted Frogs are adults. Oregon Spotted Frogs do not regon Spotted Frogs are even floating and believed to over- breed until two or three years of age. more closely tied to aquatic winter in ice-free The life span is not known, but may habitats than most of our emergent seeps, low-flow be as short as 5 years. Ofrogs and toads. On dry days, vegetation. channels or in they are found in or near the the vicinity of What do they eat? water. Even wet weather will not springs. s tadpoles, Oregon Spotted Frogs entice them far from water. This frog is Since Oregon Spotted Frogs are are grazers, their mouths equipped very easily disturbed and, if startled on not known to travel overland, their with rows of rough teeth. They feed land, will head straight to the nearest different seasonal microhabitats Aon decaying vegetation, algae and pool and dive in. If disturbed in water, must be connected by water, at least detritus. Carrion may also form part of it will dive or slowly sink below the through late winter and spring, and their diet. surface and seek refuge within vegeta- again in the fall. Roads or berms Adults and juveniles eat spiders tion or in the mucky bottom substrate. that cut through wetlands may and a wide variety of insects, includ- In general, the Oregon Spotted seriously affect population size and ing leaf beetles, ground beetles, rove Frog’s preferred habitat is warm, very distribution by hindering access to beetles, syrphid flies, long-legged shallow water with both floating critical habitats. flies, ants and water striders. Most of and emergent vegetation. Floodplain their hunting is done from the water, wetlands connected to permanent What can we do? but during and after rain showers they water are ideal habitats. Lakes, ponds regon Spotted Frogs are protected sometimes venture a few metres onto and slow-moving streams may be under British Columbia’s Wildlife land and feed among wet vegetation. used if warm shallows and emergent Act and may not be collected, kept in Oregon Spotted Frogs are best vegetation, such as grasses, sedges Ocaptivity or handled, whether as described as sit-and-wait predators. and rushes, are present. tadpoles or as adults. There are no Often remaining motionless for an Within the preferred habitat, provisions under the Wildlife Act to hour or more, they will float in a different microhabitats are required protect the Oregon Spotted Frog’s pond, half-hidden by aquatic plants at different times of year. Egg-laying habitat. Fortunately, the sites where populations are known to exist in the Fraser Valley are relatively secure at this time. In the winter of 1999, the Oregon Spotted Frog Recovery Team was formed to coordinate efforts to protect this species. The team has members from provincial, federal and regional district agencies, First Nations, universities, and conserva- . tion organizations. The team’s first Russ Haycock photo . Russ Haycock photo priority was to begin monitoring breeding sites in the Fraser Valley, and, if necessary, move egg masses to You can learn more about frogs keep them from drying out before and their habitats through BC Frog- hatching. Field surveys are also being watch, Naturescape, Wetlandkeepers continued, in hopes of discovering and Wild BC. Contact information populations that are not yet known for these programs is available or locating other potential breeding through your local Ministry of areas. The Recovery Team is also Water, Land and Air Protection office, considering reintroduction of the or check the BC Frogwatch website Oregon Spotted Frog into parts of at wlapwww.gov.bc.ca/wld/frogwatch its former breeding habitat. Team or the Stewardship Centre at members are rearing some frogs in www.stewardshipcentre.org. . captivity, to provide a genetic resevoir You can learn more about the Russ Haycock photo and animals for future reintroductions. Oregon Spotted Frog by visiting Long-term recovery of this species the Recovery Team’s website at will require public support and coop- www.oregonspottedfrog.com. eration with municipalities and regional governments, private land- owners and First Nations. , : There are many ways you can help Biodiversity Branch amphibians. Please don’t move frogs, Ministry of Water, Land and Air Protection tadpoles, or fish from pond to pond. PO Box 9374, Stn. Prov. Govt. Control non-native plant species in Victoria, British Columbia V8W 9M4 wetlands. Set up fish-free ponds as http://wlapwww.gov.bc.ca/wld part of your landscaping. Support programs to remove non-native fish and frogs from wetlands. Be careful not to let pesticides or fertilizers run into wetlands. Let local politicians and municipal planners know that endangered species are important to you. By educating yourself and then speaking up for wetland protection at municipal and --- regional district planning meetings, . , you can help ensure that Oregon Spotted Frogs will always have a place to call home in British Columbia. Printed in British Columbia on recycled paper with vegetable inks