Red-spotted Toad

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Red Spotted Toad

Red-spotted Toad

Anaxyrus punctatus (Baird & Girard, 1852)


Adults can reach to 76 mm SUL, with females (average 59 mm) larger than males (average 52 mm).  Tadpoles may reach 30 to 32 mm or more, and new metamorphs are about 13 to 18 mm SUL.  Red-spotted Toads are attractive, small anurans that can be abundant at some localities. The head is flattened, and the dorsum is brown to gray with small red spots on tubercles, these may be few or absent in old adults.  Parotoid glands are small and round. The venter is a uniform white or cream, young specimens may have some black spots in this area. Red-Spotted Toads lack the cranial crests seen in many other toad species. Larvae are black with bronze flecking and have a transparent tail. The coloration, the lack of cranial crests, and paratoid shape will separate it from most other Arizona anurans. Some spadefoots have red tipped warts but no parotoid glands.  Other Arizona bufonids that it may be confused with are juvenile Sonoran Desert Toads, however A. punctatus lacks the elongated parotoid and leg glands present in juvenile alvarius.


Voice. Males have a sing subgular vocal pouch Wright and Wright (1955) describe the call as bird-like and a high pitch trill that is pleasing.

Distribution and Habitat. The species ranges from Colorado, Arizona, Utah, Nevada, and California, southward into Mexico at elevations from below sea level to almost 2,000 m ASL. It inhabits some of the most hostile habitats in the state. It is frequently associated with rocky streams in arid terrain, although it occurs away from drainages in well-drained, rocky soils.  Activity is mostly nocturnal, but it can be found during the day by turning rocks. It is most often encountered in the Sonoran Desert Scrubland and Mojave Desert Scrubland but is found in many of the other biomes including Petran Montane Coniferous Forests.  Bradford et al. (2003) proposed that punctatus exist as patchy populations that are maintained by frequent dispersal. implying frequent dispersal between populations may prevent local extinctions (Sullivan 2005). Santos-Berra et al. (2008) found this species associated with prairie dog grasslands. It occurs in Sonoran Desertscrub (Arizona Upland Desertscrub), Mohave Desert Scrub, Chihuahuan Desert Scrub, Great Basin Desert Scrub, and Interior Chaparral, (Holycross and Brennan 2006).Diet includes most invertebrates that the toads can capture and swallow.

Smith et al. (2011) examined 20 stomachs containing prey. Ants were numerically the most important prey item in the diet followed distantly by termites and beetles. Volumetrically, beetles were the most important prey, followed by ants. Mean prey width, length, and volume were not significantly related to head length, head width, or body length. but one study suggested ants and beetles were the most frequent prey.Body temperature. Rausch et al. (2011) noted that the Red-spotted Toad is the predominant anuran in the Mojave Desert. They measured body temperature in free-ranging adult toads across all four seasons of a single year using implanted data loggers. There was marked individual variation in the temperatures experienced by these toads. As expected, toads generally escape extreme seasonal and diel temperature fluctuations. However, their data demonstrate a much wider estimated body temperature range than was previously assumed. For short periods, punctatus experience body temperatures as low as 3.1°C and as high as 39.1°C. All animals showed periods of prolonged thermal stability in cooler months and wider diel oscillations in warmer months. Red-spotted toad thermal history is likely a function of site choice; the exploitation of different refuges results in diverse thermal experiences. Reproduction occurs from March to September and timing varies with the habitat. Sonoran Desert populations use small streams to breed in the spring (March-June), while desert upland populations breed in ephemeral pools during the monsoons (June to September).  Adults spend the year in the vicinity of streams or basins where water collects when it does rain.

In central Arizona, calling males at breeding aggregations (n = 71 males sampled) ranged in size from 47–63 mm SUL.  Females in amplexus (n=8) in a single population in central Arizona ranged from 52–66 mm SUL. A population in central Arizona, had skeletochronology indicating males matured in their first or second full season following metamorphosis (Sullivan and Fernandez, 1999). Males may mature at a slightly smaller size than females after their first or second growing season.

In south-central Arizona, Red-spotted Toads breed in association with Arizona Toads, Woodhouse’s toads, Canyon Treefrogs, and Lowland Leopard Frogs in the spring, and with Colorado River Toads, Great Plains Toads, Sonoran Green Toads, and Couch’s Spadefoots in the summer (Sullivan 2005). We have also found this toad calling in association with Gastrophryne mazatlanensis.  Creusere and Whitford (1976) suggested that Red-spotted Toad larvae could not survive to metamorphosis in the presence of larvae of Spea spp. or Couch’s spadefoot toads due to heavy predation by their carnivorous larvae.

Goldberg (2016) conducted a histological examination on gonadal material from Anaxyrus punctatus from Riverside County, California. The smallest mature male (sperm in lumina of seminiferous tubules) measured 38 mm SUL and was from May. The smallest mature female (mature oocytes) measured 48 mm SUL and was from July. Varying amounts of follicular atresia (spontaneous degeneration of oocytes) was noted in all ovaries. The fecundity of A. punctatus decreased due to loss of oocytes to atresia. In Riverside County, California, A. punctatus is in breeding condition in spring and remains in reproductive condition into midsummer.

Males call from a variety of sites, including shallow water, burrows, and under rocks.  Calling activity is not always associated with rainfall, males will on extremely dry evenings when water is nowhere to be found. Males defend calling territories at breeding sites; and are separated by distances ranging from 1–3 m (Sullivan, 1984).  Amplexus-like wrestling bouts are used during territorial disputes and keep other males one to three meters away from their station (Sullivan, 1984).Breeding sites are frequently in rocky streams, springs, and shallow pools. Eggs are usually laid singly, rather than in gelatinous strands, but they may be in clumps. Egg capsules are small, 3–4 mm in diameter. Time to metamorphosis is about eight weeks. Tevis (1966) reported the number of eggs per mass varied from 30–5,000 (average 1,500).  Stebbins (1951, 1985) also described eggs as being laid in flat sheets on the bottom of ponds with the ovum being black on top and white below.

Larvae are generally black with ventral metallic bronze flecks and a translucent tail. The iris is bronze are often observed clustered in large aggregations in stream habitats, resting on muddy substrates.  In central Arizona, the larval period lasts about eight weeks in stream-breeding populations (31 March–1 June) (Sullivan 2005).Hybridization. Hybrids between Red-spotted Toads and several other species have been documented. This includes the Great Plains Toads in central Arizona (Sullivan 1990), Sonoran Green Toads in southern Arizona (Bowker and Sullivan 1991), and Woodhouse’s Toads in northern Arizona and southern Colorado (Malmos et al. 1995).  Hybrids are easily identified by their intermediate morphology and aberrant calls.

Kiesow and Griffs (2017) found tadpoles have been documented in tinajas and anthropogenic catchments and considered both critical ephemeral breeding sites for even though anthropogenic catchments can contain very high concentrations of ammonia. They tested three hypotheses of habitat selection based on resource quality: resource quality, territoriality, and proximity of water site to other water sites. Male Red-spotted Toads called from all sites regardless of habitat quality or male quality. However, they were found more often at sites within two kilometers of other sites. This suggests that male desert anurans are selecting close breeding habitat regardless of quality for breeding, indicating ammoniated sites are likely either population sinks or ecological traps. Consequently, adding anthropogenic water sites, without managing to reduce ammonia, will provide low quality habitat that could cause long-term declines in desert anuran populations.

Predators.  Predators include semiaquatic snakes, as well as birds and small mammals.  Blazquez (1996) reported predation by the watersnake Nerodia valida in Baja California, Mexico; red-spotted toads may be preyed upon by a variety of snakes, birds, and small mammals.

Defense Mechanisms. Cei et al. (1968) report the presence of presumably toxic indolealklamines from the skin and paratoid glands of Red-spotted Toads.

Fossil Record. Mead (2005) summarized the fossil record for the Red-spotted Toad. It is recorded from Deadman Cave and Wolcott Peak. Bufo sp. was recorded from Papago Springs Cave.Taxonomy. Baird and Girard, 1852:173 described Bufo punctatus based upon three syntypes (USNM 2618, three specimens) and gave no type locality. Kellogg (1932:62) later stated the type locality is Rio San Pedro [Devil’s River] of the Rio Grande Del Norte, Val Verde County, Texas, USA. Yarrow (1882:441) described Bufo beldingi based upon six syntypes (USNM 12660, six specimens) and noted USNM 1267 (4 specimens) in the original publication but they were not labelled as type material. Later (Yarrow 1882:163) did list them. One of the syntypes was exchanged to BMNH (BMNH 12660) according to Korky, (1999, 689:1) Type locality: La Paz, Baja California del Sur, Mexico. Boulenger (1883:23) synonymized this name with Bufo punctatus. Frost et al. (2006:363) used the combination Anaxyrus punctatus. Fouquette and Dubois (2014:306) used the combination Bufo (Anaxyrus) punctatus.

As currently defined, this species may represent a species complex with at least two candidate species.  Bryson et al. (2012) found evidence for three major lineages within the species.  Each of the lineages corresponded to one of the three hot desert regions.  Early speciation in Red-Spotted Toads appears to be linked to late Miocene– Pliocene development of the Baja California peninsula, followed by a Pleistocene divergence associated with the separation of the Chihuahuan and Sonoran Deserts.