Introduction

The shrew Cryptotis aroensis from Venezuela was recently described, and to date is known only from three locations in Sierra de Aroa, municipality of Bolívar, Yaracuy State: Capilla de Milla (type locality; ^{Quiroga-Carmona and Molinari 2012}), El Silencio and La Trampa del Tigre (Yurubí National Park; ^{García et al. 2013}). Nothing is known about the diet and foraging behavior of C. aroensis.

In an inventory on mammals inhabiting humid forests at Yurubí National Park, Sierra de Aroa, Venezuela (^{García et al. 2013}), an adult female of C. aroensis was captured in a pitfall trap fitted with a drift fence placed in the area known as “La Trampa del Tigre” (10° 24’ 11” N, 68° 48’ 01” W, 1,700 m). The finding of this animal offered the opportunity to document the first observations related to its activity and foraging behavior over a short period of time in captivity.

Materials and Methods

Since the capture of a living C. aroensis in the pitfall trap was unexpected (most of the time, these animals do not remain alive after being caught up in these traps), an improvised site had to be conditioned for the handling and maintenance of the shrew in the base camp at Yurubí National Park; in addition, a method was designed for the observations and collection of prey items used as food. For further details on the habitat, population and ecological aspects of C. aroensis, refer to (^{García et al. 2013}; ^{Quiroga-Carmona and Molinari 2012}).

The specimen of C. aroensis (adult; weight = 11.0 g) was placed in a plastic box (50 cm long x 35 cm wide x 35 cm high) for ten days (May 16 to 25, 2012). The box was conditioned with a thin layer of litter, log remains, bromeliads (Guzmania spp.) and mosses. Ambient temperature in the locality over the course of the experiment ranged from 10 °C at night to 25 °C in daytime. When the experiments were completed, the animal was sacrificed, processed as biological material (skin, skull and skeleton), and deposited in the Museo de la Estación Biológica de Rancho, Aragua State, Venezuela, under catalog number EBRG-29398. The scientific collection license granted by the Ministerio del Poder Popular para el Ambiente was registered under number 3411.

Potential preys were divided into three categories: soft body and size < 50 mm; hard body and size < 50 mm; and soft or hard body and size >50 mm. Prey items were placed inside the box simultaneously (every two hours from 18:00 until 06:00 hours). Most of them were offered in equal amounts, every day, and visual records were made simultaneously with a digital camera to document locomotion, posture, food preferences and prey manipulation.

Results

A total of 17 invertebrate and two small vertebrate preys belonging to three phyla and seven classes were supplied to C. aroensis (Table 1). With regard to behavior, observations were the following: at the beginning of the activity (approximately 18:00 hours), the shrew moved quickly using its four legs; no jumps were observed. Very often, it stopped to sniff out the air as well as above and under the substrate (Figure 1A, B). Then, it resumed rapid movements in a straight line over the edge and the central portion of the box; these movements were a combination of displacement above and under the litter layer. In the few moments of inactivity observed (from 20:00 hours and approximately every three hours), the shrew rested above the substrate or hidden under the litter or among small logs.

Figure 1 Transformed images of visual records that show a female of Cryptotis aroensis in the search phases and interacting with invertebrate preys (Chilopoda and Diplopoda). In images A and B, the shrew searches the area by sniffing above and below the substrate; in C, the shrew conducts searching activities and once a prey is localized, C. aroensis captures with its snout and takes it to a shelter to consume it (D). 

When a prey was detected, the shrew approached it quickly above or below the litter and captured it with the snout (Figure 1D). All capture attempts at the first encounter involved a quick bite to the anterior or posterior region of the prey’s body, immediately followed by another quick bite to attract the prey toward itself. These catches were 100 % effective in the first encounter with annelids (Annelida), sawbugs (Oniscidea), beetle larvae (Coleoptera) and geckos (Gonatodes rapicauda and Thecadactylus falconensis).

When the first bite was unsuccessful, the prey escaped (mostly Blattide, Acrididae, Gryllidae and Grillotalpa sp.), forcing the shrew to chase it; when it reached the prey, the shrew bit it repeatedly at the back portion of the body (rear end of the abdomen and legs). In other cases, C. aroensis completely ignored the prey (Opiliones, Hymenoptera, Chilopoda, Diplopoda and Lepidoptera larvae).

Prey handling for consumption consisted in tearing, cutting and chewing a small portion, and then repeating this same pattern until the prey was eaten up completely. The time taken to consume a prey ranged from two to three minutes for crickets and grasshoppers (Gryllidae), mole crickets (Gryllotalpa sp.) and cockroaches (Blattaria), up to over five minutes for the rest (Table 1).

Discussion

Under laboratory conditions, ^{Woodman and Díaz de Pascual (2004)} reported the consumption of a variety of invertebrates by a female Merida shrew (Cryptotis meridensis) observed over one month. The experiments conducted with C. meridensis documented its preference for earthworms (Lumbricus sp.); the feeding pattern involved search runs followed by patterns of circular movements and audible sounds in each of the search phases. Unlike those observations, C. aroensis showed no apparent preference for Lumbricus; during the experiments, all animals preyed upon were consumed in equal amounts, with neither patterns of circular movement nor audible sounds produced at the time of stalking and search.

Another study on Cryptotis parvus (^{Whitaker 1974}) recorded the consumption of a large amount of invertebrates, amphibians, reptiles and small mammals by the shrew. The author mentions previous studies with C. parvus specimens in captivity evidencing a behavior similar to the one observed here for C. aroensis. In most encounters of C. parvus with its prey, the latter were captured by the head; some tried to escape and were chased and bitten on the head. Others were ignored and those with a soft body were consumed completely. In all observations of C. aroensis, the shrew never used the front legs or adopted a bipedal posture for prey handling and consumption, as recorded for other small mammals with similar prey preferences (^{Martin and González-Chávez 2015}).

Some studies suggest that the external morphology of the legs among the different groups of species in the genus Cryptotis (particularly the development of the front legs with claws and humerus), provides information on their evolutionary history and food preferences (e. g., ^{Woodman et al. 2003}; ^{Woodman and Morgan 2005}). In the case of C. aroensis, ^{Quiroga-Carmona and Molinari (2012)} propose an apparent association with a more specialized diet including underground prey, due to the ease of digging provided by its developed front legs. In the trials conducted with the C. aroensis female, no direct evidence of digging or making tunnels and shelters was observed, as previously noted for the shrew C. meridensis under natural conditions (^{Díaz de Pascual and Woodman 2004}, ^{Linares 1998}), but its ability to penetrate beneath the moss layer and litter when displacing was observed.

The lack of evidence of a more underground behavior of C. aroensis is likely due to the fact that the litter-moss layer was not too thick and contained no mineral sandy or clayey soil that could restrain the movements when the shrew attempted to move under the surface. Another potential explanation is that underground preys (e. g., Lumbricus sp., Scolopendridae), did not have the opportunity to escape and hid under the substrate, so that the shrew was not forced to dig for them; or maybe the duration of the experiment was insufficient to document all possible behaviors of the species.