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Description

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Spea hammondii, the Western Spadefoot Toad, is medium-sized with adults reaching up to 65 mm in SVL. The skin is loose with small vertebral tubercles. The head is as wide as the body, having a rounded snout with an upward tilt and large protuberant eyes. The parotoid glands are small and not distinct. Forelimbs and hindlimbs are short and stout, with the foreleg having dorsal tubercles. The feet have well-developed webbing between the toes. The main distinguishing features are the single semicircular black "spade" (keratinized inner metatarsal tubercle) on each heel, and vertical pupils. The dorsal ground color ranges from light green to gray with scattered darker splotches. A pair of light-colored spots is generally present, one on each side of the anus. Body tubercles can be orange to somewhat red. Usually a pair of light-colored paravertebral stripes is present, extending from behind the eyes. Ventrally, the color is whitish to creamy-yellow.This species was featured as News of the Week on 20 July 2020: Habitat loss and degradation are the greatest causes of amphibian declines globally. A commonly proposed solution is to create artificial habitat – such as "mitigation" ponds - which can act as substitute habitat for amphibians displaced by habitat loss. But how well do they work? Baumberger et al. (2020) tested longterm success of created habitat by resurveying 21 mitigation ponds ten years post-construction and ten natural ponds impacted by urban development in southern California. They found that the artificial ponds maintained the adequate hydroperiod to sustain Western Spadefoot Toads (Spea hammondii), the species these ponds were targetting. Critically, western spadefoot larvae and embryos had been translocated to these ponds a decade earlier and many ponds still host populations which not only successfully breed but also metamorphose. These artificial habitats serve an important role because surveys found these toads are now entirely absent in the urban landscape they used to exist in. Given Western Spadefoot Toads are an IUCN Near-Threatened species, a California Species of Special Concern, and are under review for listing under the U.S. Endangered Species Act, knowing that created habitat is a successful conservation tool is critical for their conservation. Importantly, southern California is experiencing tremendous effects of climate change and these ponds were impacted by drought but provided western spadefoots a buffer against the effects of climate change. If designed correctly, artificial habitat can be a useful tool to buffer amphibian declines from both habitat loss and climate change (Written by Max Lambert). (image, http://amphibiaweb.org/images/sound3.gif) Hear calls at the Western Sound Archive (http://content.lib.utah.edu/cdm4/item_viewer.php?CISOROOT=/wss&CISOPTR=951&CISOBOX=1&REC=1).
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Distribution and Habitat

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Western spadefoot toads occur throughout the Central Valley of California into northwestern Baja California. In Baja California, they are found at least as far south as Mesa de San Carlos. They inhabit sandy areas or regions with loose soil, primarily in arroyos, fields, and open plains.
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Life History, Abundance, Activity, and Special Behaviors

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Outside of the mating season, Spea hammondii spend most of their time underground in their burrows. The Western spadefoots are mostly nocturnal creatures, but can be heard calling during the day following winter and spring rain. Mating occurs from late December to mid-May. Spadefoot toads are "explosive" breeders, taking rapid advantage of summer rains and ensuing temporary ponds to mate. Their mating call consists of a loud snore lasting 0.5 to 1 second, sounding like w-a-a-a or r-a-a-a-w. A single female can lay more than 600 eggs, attaching them to vegetation. Development can be extraordinarily rapid, with hatching occurring in as little as five days. Tadpoles are light gray to dark greenish brown in color, with a cream-colored underside and a transparent tail. The larvae have a fast growth rate and can be distinguished by their tendency to hang vertically in the water and gulp air or feed on surface material. Larvae are carnivorous and have been observed preying on other species' tadpoles as well as on conspecific tadpoles. The adult diet consists mostly of arthropods.
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Spea hammondii

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Spea hammondii, also known as the western spadefoot, western spadefoot toad, Hammond's spadefoot,[2] or Hammond's spadefoot toad,[3] is a species of amphibian in the family Scaphiopodidae.[2] It is found in western California (USA) and northwestern Baja California (Mexico). The specific name hammondii is in honor of physician and naturalist William Alexander Hammond.[3]

Description

Spea hammondii is a relatively smooth-skinned species of American spadefoot toad. Its eyes are pale gold with vertical pupils. It has a green or grey dorsum, often with skin tubercles tipped in orange, and has a whitish color on the abdomen. On each hind foot is a wedge-shaped black spade. Adult toads are between 3.8 and 7.5 cm (1.5 and 3.0 in) long. Juveniles have a similar appearance to adults, but with more distinct spotting.

Distribution

Populations of Spea hammondii are localized, but widespread. It ranges throughout the central valley of California and as far south as San Diego and some parts of the desert. The western spadefoot prefers grassland, scrub and chaparral locally but can occur in oak woodlands. It is nocturnal, and activity is limited to the wet season, summer storms, or during evenings with elevated substrate moisture levels. It is easily handled, with less skin secretions than similar toad species. Their secretions smell like peanut butter and may cause sneezing.[4] The western spadefoot is experiencing some habitat loss, but is still common in its range and the population declines are very minor even though it is listed as "near threatened" in some counties of CA.

Diet

Tadpoles feed mainly on plants and planktonic organisms, algae, ants, small invertebrates and dead aquatic larvae of amphibians, they may become cannibalistic. Adult toads feed on insects, worms and other invertebrates including; grasshoppers, true bugs, moths, ground beetles, ladybird beetles, click beetles, spiders, flies, ants and earthworms.

Life span and reproduction

The average life span for Spea hammondii is about 12 years. They reach sexual maturity in their third year. The female spadefoot toad will lay up to 2,000 eggs per season. The cordon of eggs attaches to objects in the water or puddles or ditches and the male deposits sperm on them. Tadpoles emerge in as little as 15 hours. After hatching, the tadpole's only chance for survival is to develop into a toad before the puddle dries up, which takes 12 to 13 days. This is the fastest metamorphosis known for any frog or toad. Reproduction: the breeding of laying eggs normally occur from late winter to the end of March. Males will be heard during this period. Females lay numerous small, irregular clusters that will contain from 10 up to 42 eggs. They may lay more than 500 eggs in one season. Egg to transformation may occur in 8–16 days.

Conservation

Southern California

Spea hammondii has lost up to 80% of its native habitat due to urban development within Southern California. Most of the remaining vernal pools that the toads rely on for reproduction lie on protected public land or preserves.[5] Spadefoot toads have been known to take advantage of man-made standing water sources such as road ruts, cattle ponds, and artificial pools. The species is currently under review to be listed on the federal Endangered Species Act. However, it is listed as a Species of Interest for the Central Subarea and a fully covered species for the Coastal Subarea on the Natural Community Conservation Plan (NCCP) and Habitat Conservation Plan (HCP) for the County of Orange Central and Coastal Subregion. Within this region, Spea hammondii is managed as though it is listed as a state and federal endangered species.[5]

Development in Orange County placed populations of Spea hammondii under threat, and they were relocated to newly constructed mitigation pools in 2005 and 2006. These mitigation pools are located in East Orange, Shoestring Canyon, and Irvine Mesa within Orange County Parks in the foothills of the Santa Ana mountains. A study was conducted in 2016 to monitor the reproductive success of the toads at these mitigation pools. It found that none of the five pools at East Orange or the six at Shoestring Canyon retained water during the 2016 rainy season. 12 of the 16 pools at Irvine Mesa retained water for more than 30 days. Of these 12, seven pools had successful reproduction with newly metamorphosed frogs.[6] A 1991 study found that the average duration of vernal pools that produced metamorphosed frogs was 83.1 days.[7] The soil at the East Orange and Shoestring Canyon sites was believed to be too porous to hold water, and the study recommended that soil may need to be compacted underneath the mitigation pools. Another suggestion was use an artificial lining under the pools to hold water. Overall, it was concluded that the mitigation pools were successful with a surviving population of Spea hammondii after 10 years.[6]

A restoration project began in 2019 with a partnership between the California Department of Fish and Wildlife, California State Parks, Orange County Parks, and the Natural Communities Coalition to create 16 artificial breeding pools across Crystal Cove State Park and Laguna Coast Wilderness Park.[8] The pools are expected to be completed in 2023.[8] Ten pools will be lined with clay, while the other six will be lined with PVC to study differences in water retention.[9] The project also will restore 15 acres of coastal sage scrub around the pools to provide foraging areas for the spadefoot toads, as well as nesting opportunities for the cactus wren.[9]

References

  1. ^ IUCN SSC Amphibian Specialist Group (2022). "Spea hammondii". IUCN Red List of Threatened Species. 2022: e.T59045A53972800. doi:10.2305/IUCN.UK.2022-2.RLTS.T59045A53972800.en. Retrieved 12 May 2023.
  2. ^ a b c Frost, Darrel R. (2019). "Spea hammondii (Baird, 1859)". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 5 March 2019.
  3. ^ a b Beolens, Bo; Watkins, Michael & Grayson, Michael (2013). The Eponym Dictionary of Amphibians. Pelagic Publishing. p. 89. ISBN 978-1-907807-42-8.
  4. ^ Conant, Roger. 1975. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Houghton Mifflin. Boston.
  5. ^ a b Neal, Kevin M; Fisher, Robert N; Mitrovich, Milan J; Shaffer, H Bradley (31 December 2020). Garrick, Ryan (ed.). "Conservation Genomics of the Threatened Western Spadefoot, Spea hammondii , in Urbanized Southern California". Journal of Heredity. 111 (7): 613–627. doi:10.1093/jhered/esaa049. ISSN 0022-1503.
  6. ^ a b Baumberger, Katherine L.; Backlin, Adam R.; Gallegos, Elizabeth A.; Hitchcock, Cynthia J.; Fisher, Robert N. (25 May 2020). "Mitigation Ponds Offer Drought Resiliency for Western Spadefoot (Spea hammondii) Populations". Bulletin, Southern California Academy of Sciences. 119 (1): 6. doi:10.3160/0038-3872-119.1.6. ISSN 0038-3872.
  7. ^ Morey, Steven R.; Reznick, David N. (January 2004). "The relationship between habitat permanence and larval development in California spadefoot toads: field and laboratory comparisons of developmental plasticity". Oikos. 104 (1): 172–190. doi:10.1111/j.0030-1299.2004.12623.x.
  8. ^ a b "Project: Western Spadefoot Habitat Restoration and Seasonal Pool Creation". California Natural Resources Agency. 9 May 2023. Retrieved 9 May 2023.{{cite web}}: CS1 maint: url-status (link)
  9. ^ a b Nguyen, Lilly (12 December 2019). "Coastal Commission approves 8 toad pools and habitat restoration at Crystal Cove State Park". Los Angeles Times. Retrieved 9 May 2023.{{cite web}}: CS1 maint: url-status (link)
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Spea hammondii: Brief Summary

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Spea hammondii, also known as the western spadefoot, western spadefoot toad, Hammond's spadefoot, or Hammond's spadefoot toad, is a species of amphibian in the family Scaphiopodidae. It is found in western California (USA) and northwestern Baja California (Mexico). The specific name hammondii is in honor of physician and naturalist William Alexander Hammond.

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