Thyroptera tricolor

Geographic Range

Spix's disk-winged bats ( Thyroptera tricolor ) are native to the Neotropical region. Their range extends from southern Mexico, through most of Central America, and into South America as far as northern Bolivia. In South America, their range extends as far west as Ecuador and Peru, east of the Andes mountains. Their range continues east through forested regions of Bolivia and Brazil, and along most of coastal Brazil. Their range also includes other countries in northern South America, such as Colombia, Guyana, Suriname, French Guiana, Trinidad and Tobago, and parts of Venezuela.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Spix's disk-winged bat inhabit tropical regions. They are typically found at elevations from 0 to 600 m above sea level (asl), but have been reported in areas up to 1800 m asl. They are found in forests, rainforests, and montane regions.

Spix's disk-winged bat roost in rolled-up leaves of native trees, such as lobster-claws (genus Heliconia ). Young leaves of such trees naturally curl into cone shapes, with a small opening (40 to 100mm in diameter) at the end of each leaf. Because lobster-claw leaves quickly unroll as they grow, Spix’s disk-winged bats change roost sites frequently.

• Habitat Regions
• tropical tropical

• Terrestrial Biomes
• forest forest
• rainforest rainforest
• mountains mountains

Physical Description

Adult Spix's disk-winged bats are 67 to 79 mm long, from head to tail, and have body masses from 3.4 to 5.1 g. They have dark brown dorsal pelage, and lighter, cream-colored ventral pelage. Spix's disk-winged bats have conspicuous circular pads on their thumbs and hind feet. These pads function similarly to suction cups, allowing Spix's disk-winged bats to adhere to flat surfaces, such as the leaves of lobster-claws (genus Heliconia ), where they tend to roost.

Spix's disk-winged bats exhibit some sexual dimorphism. Adult females weigh more (average body mass = 4.0 g) and have longer forearms (average forearm length = 37.1 mm) compared to adult males (average body mass = 3.7 g; average forearm length = 36.7 mm). Adult males have longer tails (average tail length = 28.6 mm) and hind feet (average hind foot length = 5.9 mm) than females (average tail length = 27.3 mm; average hind foot length = 5.7mm). Both sexes have similar average ear lengths of around 12.3 mm. Spix's disc-winged bats have 38 teeth, with a dental formula of 2133/3133.

Spix's disk-winged bats are born hairless, and reach average adult mass at around seven months. Birth mass of young is dependent on the mass of pregnant females. In general, the mass of a newborn is 26 to 31% of the mass of its mother prior to pregnancy.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

The re is limited information regarding the mating systems of Spix's disk-winged bats. Although it is suspected that they are polygynous, males do not exhibit mate-guarding behaviors typical of other tropical, polygynous bat species. Because Spix's disk-winged bat change roosting sites often, they do not defend specific locations or social groups.

Spix’s disk-winged bats and tend to stay within the same home range and social groups throughout their lives, but manage to avoid inbreeding. Although they typically have low dispersal rates, males may travel up to 500 m away to breed with females in separate social groups. Genetic studies have also reported low levels of relatedness between males and females within social groups.

Spix's disk-winged bats use contact calls to find potential mates. Males fly around emitting mating calls, and receptive females respond to these calls from their roosting sites, typically in the rolled leaves of lobster-claws (genus Heliconia ).

Spix’s disk-winged bats are iteroparous, with a mating season between August and September. Females gestate their young for 3.5 to 4 months, and nurse their pups for another 4 months. Females produce one offspring per breeding season and the birth mass of pups typically is 26 to 31% the mass of their mothers. Juveniles reach independence after approximately 4 months, but are volant after 2 months. Males reach sexual maturity within one year, whereas females reach sexual maturity within two years.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Female Spix's disk-winged bats protect and nurse their young for about 4 months following parturition. Due to the ephemeral nature of the roosts that Spix's disk-winged bats use, mothers transport pre-volant pups between different heliconia (genus Heliconia ) leaves frequently. Males provide no parental investment beyond the act of mating. There is a low dispersal rate within bats of the same natal group, suggesting that Spix's disk-winged bats show some level of maternal association following independence.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-weaning/fledging
  • provisioning
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female
• post-independence association with parents

Lifespan/Longevity

There is currently no reported lifespan for Spix's disk-winged bats, or any other bats in the genus Thyroptera . However, a study from 2013 estimated mean lifespan using survivorship rates across three age groups: juveniles (< 1 years old), prime-age adults (2 - 3 years old), and senescent adults (> 4 years old). In this study, senescent adults had the lowest annual survival rate (0.45), followed by juveniles (0.55) and then prime-age adults (0.77). Based on these survivorship, the mean lifespan Spix's disk-winged bats of in the wild was estimated at 2.81 years. There are no reports of Spix's disk-winged bats being kept in captivity and therefore no reports of captive lifespans.

Behavior

Spix's disk-winged bats form and maintain social groups over long periods. Within social groups, individuals form pairs which maintain contact for as long as 400 consecutive days. Spix's disk-winged bats maintain group cohesion by emitting contact calls, which allow group members to recognize one another. Spix’s disk-winged bats roost in groups of up to six bats. Social groups are composed of males and females, but groups are slightly male-biased on average. Though there is no clear hierarchy, both male and female bats tend to associate more strongly with other males. Male and female bats of the same social group never mate, but maintain non-sexual associations.

The ephemeral nature of their roosting sites influences the movements of Spix's disk-winged bats. Though they have strong ties within social groups, it is rare for all members to roost in the same leaf every night. Although Spix's disk-winged bats exhibit fission-fusion dynamics within their social group, they typically avoid interaction with other social groups outside of breeding season.

Spix’s disk-winged bats are nocturnal insectivores. They forage for food and move between roost sites at night. When choosing new roost sites, Spix's disk-winged bats typically choose longer leaves (average leaf length = 122.0 cm) with smaller leaf-mouth diameters (average diameter = 13.2 cm). Longer leaves provide space for more roosting bats, while smaller leaf-mouth diameters help conceal bats from predators and insulate them from fluctuating temperatures. Tighter rolled leaves also better amplify the contact calls that roosting bats emit to communicate with flying bats.

• Key Behaviors
• flies
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• social social

Home Range

Spix’s disk-winged bats have an average home range of 1780 m^2 (range = 70 - 6200 m^2). The inherent fission-fusion dynamics of social groups means that Spix's disk-winged bats typically have overlapping home ranges. There is no consistent difference between home range sizes of Spix's disk-winged bats based on sex. They do not defend specific territories, as they usually change roosting sites every night.

Communication and Perception

Spix’s disk-winged bats rely heavily on acoustic stimuli to communicate and perceive their environment. They communicate with conspecifics using echolocation and contact calls. Their echolocation calls are low intensity, with frequencies averaging 45 kHz, and short range, suggesting that Spix’s disk-winged bats hunt by gleaning insects off of surfaces.

Spix’s disk-winged bats use contact calls to identify conspecifics at roosting sites. Bats in flight make contact calls, which nearby roosting bats detect and respond to with their own contact calls. Contact calls are suspected to be specific to individuals, allowing Spix’s disk-winged bats to identify others within their social group, as well as potential mates outside of their social group. The specificity of contact calls also allows parents to identify their pups. The frequency of contact calls between males and ovulating females is relatively high, suggesting that reproductive cycles influence how receptive roosting female bats are to flying male bats.

Spix’s disk-winged bats also use visual and tactile stimuli to communicate and perceive their environment. They use touch to capture prey and to communicate with pups or potential mates. They also have well-developed vision in low light, which they use to capture prey, find mates, and communicate within roosts. Spix's disk-winged bats also detect chemical stimuli, such as pheromones released by conspecifics.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• echolocation echolocation
• chemical chemical

Food Habits

Spix’s disk-winged bats are primarily insectivores. While they sometimes consume prey by aerial hawking, they mostly glean insects off of surfaces, such as leaves or the trunks of trees. Spix’s disk-winged bats are considered opportunistic feeders.

A study from 2006 found that the diets of Spix’s disk-winged bats consisted primarily of non-volant arthropods across two classes and nine orders. The frequency of occurrence for different insect groups in fecal pellets varied widely. However, 93% of pellets contained jumping spiders (family Salticidae ), 81% contained leafhoppers (family Cicadellidae ), 63% contained adult moths and butterflies (order Lepidoptera ), and 59% contained true flies (order Diptera ). Insect larvae from the orders Hymenoptera and Lepidoptera were present in 43% of fecal pellets, and fecal pellets also included adult beetles (29%; order Coleoptera ), earwigs (28%; order Dermaptera ), hymenopterans (25%; order Hymenoptera ), and lacewings (23%; order Neuroptera ).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods

• Animal Foods
• insects
• terrestrial non-insect arthropods

Predation

Spix's disk-winged bats are most vulnerable to predation while changing roosts. To minimize exposure to predators during this time, flying bats emit contact calls, which roosting bats respond to with their own contact calls. Individuals vary in their responsiveness to contact calls, but the amount of energy expended by flying bats is inversely related to the amount of vocalizations emitted by roosting bats. Because vocalization requires energy, physical wellness and reproductive status both influence the amount that roosting bats vocalize. For example, lactating bats are the least likely to respond to calls from flying bats, as any response puts them at higher risk of predation.

Spix’s disk-winged bats have cryptic coloration that helps them avoid predation. Furthermore, their preferred roosting sites in rolled-up Heliconia leaves provides them natural cover from predators. Known predators of Spix’s disk-winged bats include hawks (genus Buteo ), falcons (genus Falco ), white-faced capuchin monkeys ( Cebus imitator ), raccoons ( Procyon lotor ), and South American coatis ( Nasua nasua ).

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Spix's disk-winged bats are primarily insectivores and likely play a role in controlling populations of prey species. They also serve as a source of prey for falcons, monkeys, and other diurnal predators.

Spix's disk-winged bats are hosts for ectoparasitic flesh flies ( Sarcofahrtiopsis thyropteronthos ), which live on their wings and are also found in their roost sites.

Economic Importance for Humans: Positive

There are no known positive economic impacts of Spix's disk-winged bats on humans.

Economic Importance for Humans: Negative

There are no known negative economic impacts of Spix's disk-winged bat on humans. Although they may be capable of carrying and transmitting rabies, no cases have been confirmed in Spix’s disk-winged bats and serum sample tests on 2 individuals were negative.

Conservation Status

Spix's disk-winged bats are listed as a species of “Least Concern” on the IUCN Red List. They have no special status on other national or international conservation lists.

There is growing concern about the conservation status of Spix’s disk-winged bats as climate change and anthropogenic development continue to disrupt or destroy their habitat. Globally, 24% of bat species are under threat from human activities, and highly specialized species, such as Spix's disk-winged bats, are under greater threat compared to generalist species. They primarily roost in young, rolled-up leaves of Heliconia plants, which puts them at risk of future endangerment if the availability of these roost sites decreases.

There are populations of Spix’s disk-winged bats in national parks in South America, providing them some level of protection by the conservation laws associated with national parks. However, no species-specific conservations efforts are currently in place.

Additional Links

Encyclopedia of Life

Contributors

Waitta Jarso (author), Radford University, Sierra Felty (editor), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor), Special Projects.

References

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