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Alytes obstetricans

By Jacquelyn Albert

Geographic Range

Common midwife toads occur in southern Belgium, most of France, western and north-central Germany, Luxembourg, the southeastern Netherlands, northern Portugal and Spain, and northwestern Switzerland; with at least one introduced population in the UK. Populations are reported to be declining and in some areas populations appear to be completely eradicated, such as in coastal Portugal (west of Lisbon). Populations are particularly fragmented in Spain and Portugal but common midwife toads are still common throughout many areas, particularly France. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife Toad Conservation", 2012; Bosch, et al., 2009; Van der Meijden, 2010)

Habitat

Common midwife toads are primarily terrestrial, inhabiting a wide range of habitats such as temperate forests and semi-arid areas. They successfully reside in human-modified habitats, such as agricultural plots and urban areas (ex: Barcelona). This species prefers areas with slopes, walls, or embankments with sparse vegetation and many small stones. They are often found hiding in the crevices of these structures, under logs, or underground in pre-existing burrows of other animals, in order to prevent from drying out. Aquatic habitats are only required for breeding. There is a wide range of appropriate aquatic habitats for breeding from ponds to slow moving rivers, and occasionally gravel or clay pits. Permanent waters are preferred because larvae over-winter in water. ("Common midwife toad (Alytes obstetricans)", 2014; Bosch, et al., 2009; Van der Meijden, 2010)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range elevation
    0 to 2400 m
    0.00 to 7874.02 ft
  • Average elevation
    200-700 m
    ft

Physical Description

Common midwife toads are not "true toads"; they are frogs with warty skin and stout toad-like bodies. Their fingers are short and un-webbed and they have long toes that are only webbed at the base. Their bodies are covered in reddish warts; the warts are particularly prevalent on the ankles, underarms, and in a line from the eardrum to the groin. Body coloration can be quite varied, ranging from pale to brown. The underside is an off-white color. The spots on the throat and chest can be many colors including black, brown, olive, green or grey. They have vertical slit-shaped pupils in their large eyes. The parotoid glands are small, with a mostly visible tympanum. Common midwife toads have three metacarpal tubercles. Males are smaller than females, growing to 42 mm in length, as opposed to females, which can grow to 50 mm. ("Common midwife toad (Alytes obstetricans)", 2014; Bosch and Marquez, 1996; Van der Meijden, 2010)

  • Sexual Dimorphism
  • female larger
  • Range length
    25 to 50 mm
    0.98 to 1.97 in

Development

Eggs are carried on the male’s body until they hatch. Tadpoles are then deposited into small permanent bodies of water. Larvae are originally about 15 mm long and reach surprisingly large sizes. They metamorphose when they reach a length of 5 to 8 cm, which occurs after about a year. Sexual maturity occurs at 2 to 3 years of age for both males and females. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife toad Facts", 2014; Van der Meijden, 2010)

Reproduction

Common midwife toads get their common name from their unique mating system. Males carry eggs on their bodies until the eggs hatch and then the males release the tadpoles into a body of fresh water (often permanent water because tadpoles must over-winter). Males call mainly at night about every 1 to 3 seconds with a high-pitched “poo…poo…” sound. Once a female locates a male and presents herself, the male will grab the female around her lumbar region and begin stimulating her cloaca with a scratching motion of his toes. The female will then expel an egg mass that is subsequently fertilized by the male’s ejection of a liquid sperm mass. Inseminated eggs are then wound around the male’s ankles. ("Midwife Toad", 2012; Van der Meijden, 2010)

Sexual maturity occurs at about 12 to 18 months. Mating seasons vary throughout the toad’s range and egg-carrying males can be found anytime between the end of March and the beginning of August. By carrying the eggs, male toads are able to keep them out of the water, where the eggs are in high danger of getting eaten. Males can carry about 150 eggs around their ankles during one breeding season, which is equivalent to about three clutches. Females can produce up to four clutches per breeding season. Males keep the eggs moist by choosing appropriate microhabitat and occasionally taking freshwater “baths.” After 3 to 6 weeks the eggs hatch and the tadpoles are deposited by the male into a small body of water. ("Midwife toad Facts", 2014; Van der Meijden, 2010)

  • Breeding interval
    One breeding season a year, capable of multiple partners or broods in a year
  • Breeding season
    Breeding occurs between March and August.
  • Range time to hatching
    3 to 6 weeks
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

After fertilization, males carry the eggs on their hind-legs until they hatch. After hatching, males carefully deposit the larvae into small, permanent bodies of water. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife Toad", 2012; "Midwife toad Facts", 2014; Van der Meijden, 2010)

  • Parental Investment
  • male parental care
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male

Lifespan/Longevity

Common midwife toads live up to eight years in the wild. ("Midwife toad Facts", 2014)

  • Range lifespan
    Status: wild
    8 (high) years
  • Average lifespan
    Status: wild
    5 years

Behavior

Common midwife toads are highly terrestrial, only living in the water as tadpoles. They are also nocturnal and often hide in holes or under logs to prevent from drying out. If an individual can not find a pre-existing hole, it uses its forelimbs and head to dig its own burrow, then it uses a "push-up" like motion to pack soil over the head, creating a roof for the hole. Common midwife toads typically exit their burrows at dusk to forage for insects and other arthropods. Adults are able to terrestrially hibernate under frost-protected ground during winter months. During the breeding season, males call every night for several hours. Occasionally, males can be heard calling from their burrows during the day. Females tend to prefer males who call frequently. Females give a response call to the male of her choice, which is uncommon amongst other anurans. Competition between males during the breeding season is strictly vocal, with no aggression between individuals observed. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife Toad Conservation", 2012; "Midwife Toad", 2012; Marquez, et al., 2010; Van der Meijden, 2010)

Home Range

These toads typically stay close to bodies of water, but they have been observed up to 500 meters away from these water bodies. (Van der Meijden, 2010)

Communication and Perception

Food Habits

Common midwife toads eat mostly eats insects and other arthropods. They emerge from their burrows at dusk and begin to feed on beetles, maggots, caterpillars, woodlice, spiders, slugs, snails, millipedes, worms, harvestmen, and others. After foraging, they return to their hiding space before dawn. Common midwife toads have sticky tongues used to capture prey and tiny horny teeth used for chewing. Tadpoles are herbivores and feed on aquatic plants and other plant debris. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife Toad", 2012)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms

Predation

When common midwife toads are threatened, they excrete a potent smelling toxin from the warts on their back to defend against predators. This toxin is enormously effective and can be deadly; within hours the toxin can kill an adder (venomous snake). Tadpoles cannot yet produce this toxin and are vulnerable to predators during their development. Fish and aquatic insects feed on tadpoles. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife Toad", 2012)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Common midwife toads are undoubtedly host to various internal and external parasites, but the most serious threat to date is chytrid fungus. (Bosch, et al., 2009)

Economic Importance for Humans: Positive

Common midwife toads may benefit humans by consuming arthropod pests. This species has also been used to research Lamarckian inheritance or epigenetics. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife Toad", 2012; Bosch and Marquez, 1996; Van der Meijden, 2010)

  • Positive Impacts
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

This species is harmless to human interest and values, unless ingested.

Conservation Status

Although common midwife toads are considered "least concern" (IUCN) and are still common and widespread in some areas, they are experiencing population declines as well as some localized extinctions. They are listed on Annex IV of the EU Habitats Directive as well as on Appendix II of the Bern Convention. Common midwife toads are protected by national legislation throughout much of their range and are considered "near threatened" on the Spanish national Red List. Central Spain has begun employing captive breeding programs as well as reintroductions. Potential reasoning for population declines could be general habitat loss, especially habitat lost to farming and degradation of breeding sites. Many habitats are fragmented which can cause population decline and loss of gene flow. Chytridiomycosis infection, caused by a fungal parasite, is becoming more common, causing some populations to severely decline or even disappear. Iridovirus and "red-leg disease" has also been reported in declining populations in recent years. Introductions of predatory fish, such as salmonids, into breeding pools has also become a considerable threat, particularly to hatchlings and tadpoles. ("Common midwife toad (Alytes obstetricans)", 2014; "Midwife toad Facts", 2014; Bosch and Marquez, 1996; Bosch, et al., 2009; Marquez, et al., 2010; Van der Meijden, 2010)

Contributors

Jacquelyn Albert (author), Michigan State University, James Harding (editor), Michigan State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

breeding is confined to a particular season

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

References

2014. "Common midwife toad (Alytes obstetricans)" (On-line). Evolutionarily Distinct and Globally Endangered. Accessed December 02, 2014 at http://www.edgeofexistence.org/amphibians/species_info.php?id=1374.

2012. "Midwife Toad Conservation" (On-line). World Association of Zoos and Aquariums. Accessed December 02, 2014 at http://www.waza.org/en/site/conservation/waza-conservation-projects/midwife-toad-conservation.

2012. "Midwife Toad" (On-line). LadyWildLife. Accessed December 02, 2014 at http://ladywildlife.com/viewmainpageinfo.php?pid=midwifetoad.

2014. "Midwife toad Facts" (On-line). Soft School. Accessed December 02, 2014 at http://www.softschools.com/facts/animals/midwife_toad_facts/1062/.

Bosch, J., R. Marquez. 1996. Discriminant functions for sex determination in two midwife toads (Alytes obstetricans and A. cisternasii). Herpetological Journal, 6: 105-109.

Bosch, J., T. Beebee, B. Schmidt, M. Tejedo, I. Martinez-Solano, A. Salvador, M. Garcia-Paris, E. Recuero Gil, J. Willem Arntzen, C. Diaz Paniagua, R. Marquez. 2009. "Alytes obstetricans (Common Midwife Toad)" (On-line). IUCN Red List. Accessed December 02, 2014 at http://www.iucnredlist.org/details/55268/0.

Marquez, R., J. Bosch, X. Eekhout. 2010. Intensity of female preference for call source level in midwife toads Alytes cisternasii and A. obstetricans. Behavior, 147(9): 1185-1199.

Van der Meijden, A. 2010. "Alytes obstetricans" (On-line). AmphibiaWeb. Accessed December 02, 2014 at http://amphibiaweb.org/cgi/amphib_query?where-genus=Alytes&where-species=obstetricans.

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