Familia Ctenomyidae (Lesson, 1842)
Este grupo exclusivamente Sudamericano, comprende a roedores caviomorfos subterráneos, comúnmente llamados tuco-tucos, untutucos, ocultos, tunducos, entre otros nombres vulgares. Cuenta con alrededor de 60 especies vivientes agrupadas en un solo género Ctenomys (Blainville 1826). Se distribuyen por gran parte de Sudamérica, desde el sur de Perú, Bolivia, Paraguay, sur de Brasil y Chile, hasta el sur de la Patagonia Argentina, siendo este último país el que cuenta con más especies descriptas. Ocupan gran variedad de hábitats, desde desiertos costeros, bordes salinos, sistemas de dunas al nivel del mar y sabanas, hasta altiplanicies de más de 5000 msnm. El nombre que da origen a la familia taxónómica proviene del griego “ktenos” = peine; “mys”=ratón, en alusión a cerdas rígidas que presenta en el borde externo de las patas traseras, las cuales se asemejan a un peine.
Descrição morfológica: Apresentam adaptações anatômicas associadas à vida subterrânea, com corpo cilíndrico, membros anteriores e posteriores curtos e robustos, além de cauda relativamente curta, olhos pequenos e orelhas reduzidas. Por sua vez, apresentam um crânio forte e compacto, dotado de grandes incisivos de coloração alaranjada em sua parte frontal (com exceção de C. leucodon). Seu tamanho varia, com espécies pequenas de alguns poucos gramas como C. pundti, até espécies de tamanho considerável como C. conoveri podendo atingir um quilograma ou mais. Assim como o tamanho, a coloração do pelagem varia de acordo com a espécie, geralmente com variações de tons marrons escuros a claros, e tonalidades amareladas, embora também existam registros de indivíduos melanísticos e colorações acinzentadas. Além disso, apresentam dimorfismo sexual sendo o macho maior que a fêmea, diferença que se acentua na idade adulta.
Natural history: They are mostly solitary species, however, different degrees of sociability have been determined, with species showing an intermediate degree of interaction between individuals ( C. opimus ), and others with a complex social structure ( C. sociabilis ). They have a generalist herbivorous diet, consisting of woody shrub vegetation, roots, and grasses, although some species apparently prefer the latter. They build extensive underground tunnels in open areas (although some species also inhabit forested zones) usually occupied by a single adult (except in C. sociabilis). These tunnels can vary in structure and size, covering large areas and reaching depths between 30 and 65 cm ( C. mendocinus ). Generally, these systems have a main linear gallery, with several branches leading to chambers inside, and numerous tunnels with accessory exits scattered on the surface. They dig on the ground with their forelimbs, complementing this activity with their incisors, which protrude from the oral cavity to prevent the entrance of soil and particles during digging. However, this mechanism appears to be related to the hardness of the substrate, being more frequent in hard and compact soils than in loose and/or sandy soils. They exhibit both diurnal and nocturnal habits, and rarely emerge to the surface. They make incursions outside their burrows in search of food, which they transport back into their tunnels for storage or consumption. They also feed on roots and tubers from inside their tunnels as they dig, and near burrow entrances, where branches and shrub stems with incisor marks can often be observed. Additionally, their presence is indicated at the entrances of their tunnels when active, with fine dirt mounds or remnants of food and feces near the entrance. However, when the individual is inside the burrow, they block the entrance with dirt. The tunnels are maintained and checked constantly, due to the stable microclimatic conditions (temperature, humidity, gas concentrations, among other parameters) that underground life imposes. The ventilation of the tunnels is key to avoiding excessive carbon dioxide accumulation, so tunnel blockages are made with porous and loose substrate and/or with vegetation and feces, allowing air currents to flow in. As they are generally solitary species, encounters or interactions with other individuals are limited to mate searching, offspring care, and territorial conflicts, which tend to be aggressive in nature.
Vocalizations: Most species produce vocalizations consisting of deep sounds resembling drums, whose onomatopoeia is described as “tuca-tuc,” and from which their common names derive. Both males and females vocalize, though the latter to a lesser extent. There are also different types, which vary in intensity and duration. These vocalizations play a crucial role in communication between individuals, being used to mark territory and maintain social groups.
Predadores: Os tuco-tucos são presas frequentes tanto para aves quanto para mamíferos. Entre seus predadores aviários mais frequentes, podemos citar a coruja comum ( Tyto furcata ), a corujinha de vizcacheras ( Athene cunicularia ), o corujão de campo ( Asio flammeus ), a águia mora ( Geranoaetus melanoleucus ), gaviões (gêneros Buteo e Geranoaetus ) e falcões (gêneros Falco) entre outros. Entre os mamíferos, há registros de predação por parte do zorro cinza ( Lycalopex gymnocercus ), o furão menor ( Galictis cuja ), a comadreja ( Didelphis albiventris ), o zorrino comum ( Conepatus chinga ) e o quirquincho pequeno ( Chaetophractus vellerosus ), e além disso, existe uma espécie aparentemente especializada em sua captura, o furãozinho ( Lyncodon patagonicus ). Também há registros de predação por parte de serpentes do gênero Bothrops.
Importance and threats: Like other fossorial mammals, they are considered "ecosystem engineers," as they act as agents shaping natural systems, due to their ability to modify the environment, altering organic properties of the soil, nutrient availability and redistribution, and other resources. They also promote the establishment of other species by increasing terrain heterogeneity, creating new habitats, which could influence the dynamics of plant communities and fungi through seed and propagule dispersal. Taxonomy, like many aspects of this group’s biology, is complex and constantly under study and debate, with species having non-overlapping distributions and wide ranges, while others represent endemisms with poorly defined limits, known from few records. Tuco-tucos have high habitat specificity, occupying areas with sandy, friable, and permeable soils, which in nature are generally arranged in isolated patches. Because of this, their specific life requirements, limited dispersal, and solitary habits place them in a position of high dependence on the quality of the environment they occupy, meaning that habitat loss, degradation, and fragmentation due to land use changes represent their major threats.
Author of this compilation: Enzo Rossi - 17/06/2021
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