DOI: 10.5061/dryad.vx0k6djn9
title: Predator-prey interactions in anurans of the tropical dry forests of the Colombian Caribbean: a functional approach

description: Anuran–prey selection might be mediated by traits, either by mismatches in
 predator and prey traits (preventing interactions) or by predator
 selection of prey traits (encouraging interactions). These effect traits
 could be summarized in two contrasting foraging strategies: “active” and
 “sit‐and‐wait” foragers. We evaluated whether anurans could be classified
 into groups of species sharing traits associated with their diet, and what
 is the relation between particular effect traits of anurans and their
 prey. We collected anurans and identified their stomach contents once
 during dry, minor, and major rain seasons in six dry forest sites in the
 Colombian Caribbean. For each of the 19 anuran species and 436 prey items,
 we registered six effect traits. We applied RLQ and fourth‐corner
 methodologies to relate predator and prey traits through their interaction
 matrix. Predators were assigned to five groups according to their
 differences in locomotion, body shape, proportion of the jaw width, mode
 of tongue protrusion, and strata preferred. Regarding preys, species were
 assigned to four groups according to their gregariousness, body shape and
 hardness, defensive traits, and mobility. Body size of both, predators and
 prey, had a minor contribution in the group assignment. We found that
 predators using active search target low‐mobility preys, whereas species
 using sit‐and‐wait strategy target highly nutritive prey that are
 difficult to manipulate. By linking amphibian diet with foraging
 strategies, we hope to contribute to the understanding of mechanisms
 behind anuran–prey food web patterns and to build more realistic models of
 functional response to changing environments.
description: We collected anurans and identified their stomach contents once
 during dry, minor and major rain seasons in six dry forest sites in the
 Colombian Caribbean. For each of the 19 anuran species and 436 prey items,
 we registered six effect traits. We applied RLQ and Fourth-corner
 methodologies to relate predator and prey traits through their interaction
 matrix. We sampled six sites within the tropical dry
 forests of the Colombian Caribbean. The sites were located between
 11°5'26.68" N - 72°38'38.84" W and
  8°47'35.24" N - 76°19'43.31" W, and separated, on
 average, by a linear distance of 115.3 km. Local elevation was less than
 500m above sea level, and the region included both forest remnants and
 intervened areas. We surveyed each site during the dry season
 (February-March), at the onset of "minor rains" (May-June), and
 during the rainier season (October-November). Each visit consisted of
 two-hour searches for five nights between 1900 h and 2300 h. During each
 search, we encountered anurans through visual surveys,
 collected every recorded specimen, and preserved the specimens according
 to Angulo <i>et al.</i> (2006). We collected a minimum of five
 and a maximum of 146 (mean ± SD = 58.2 ± 39.1) individuals per species,
 focusing on adult and sub-adult specimens only. With that, we avoided the
 interference from changes in the diet that take place when juveniles
 become sub-adults. It must be noted that the same analyses excluding
 sub-adult specimens gave similar results (Blanco-Torres pers.
 comm.). In the laboratory, we screened the stomach
 content of each specimen collected, registering the number of individuals
 per prey item. Arthropod preys were identified at the level of species or
 morphospecies by specialists at the Universidad Nacional de Colombia and
 Universidad del Atlántico-Colombia. Voucher specimens were deposited in
 Universidad del Atlántico’s museum We selected and
 quantified six predator effect traits that are known to influence food
 intake by species, as per Trochet <i>et al.</i> (2014), Vitt
 & Caldwell (2014) and Cortés Gómez <i>et al.</i>
 (2015) (Table S1). Morphological traits included: 1) body size (S), as the
 snout-vent length (range: 7-131 mm), 2) body / jaw size ratio (SJ, range:
 1-6.03), calculated as the proportion of the jaw width (as the horizontal
 length of the open mouth cavity measured from collected specimens)
 relative to the body length, 3) body shape (BS), assigned to the more
 similar geometric shape of the contour of the predator body, and
 classified according to four categories: BS1: pointed-elongated; BS2:
 ovoid; BS3: elongated; BS4: rounded-pointed (Fig. S1), 4) locomotion mode
 (LM), which classified species as burrowers (LM1), walkers (LM2), hoppers
 (LM3), terrestrial jumpers (LM4) or arboreal jumpers (LM5) after Reilly
 & Jorgensen (2011), 5) tongue protrusion mode (T), classified as
 mechanical expulsion of the tongue through muscle contraction (K1),
 inertial elongation (K2), or hydrostatic elongation (tongue lengthened
 through volume limitations imposed by the constant volume of an
 hydrostatic muscle, K3), after Nishikawa (1999), 6) preferred strata
 classified as terrestrial (H1), arboreal (H2), or cave dwelling (H3),
 based on our own surveys
 and confirmed through bibliography (e.g., Renjifo &
 Lundberg 1999, Cuentas <i>et al.</i> 2002, Blanco-Torres
 <i>et al.</i> 2019). We also quantified six
 prey effect traits: 1) body shape (bs), assigned to the more similar
 geometric shape of the contour of the prey body, according to the
 following categories: rectangular (bs1), circular (bs2) or ovoid (bs3;
 Fig. S2), 2) body hardness (bh), classified according to the level of
 sclerotization as soft (bh1), medium (bh2) or chitinous (bh3), 3) size
 (s), measured from the specimens obtained from the stomach content
 analysis (range:1-1600 mm<sup>3</sup>), 4) mobility (m), based
 on the presence and type of legs, and the presence of wings, the prey
 specimens were classified as larvae (m1), walkers (m2), jumpers (m3) and
 flyers (m4), after Speight<i> et al.</i> (2008) and Triplehorn
 & Johnson (2005), 5) defense type (d), which was classified as:
 chemical (d1), mechanical (d2), or inexistent (d3), based on the most
 frequent defense type within the genus or, in most cases, family level,
 after Speight<i> et al.</i> (2008) and Triplehorn &
 Johnson (2005), and 6) gregariousness (g), according to the social
 structure of species, genus or family, classified as gregarious (g1) or
 not gregarious (g2), after Speight<i> et al.</i> (2008) and
 Triplehorn & Johnson (2005). Whenever the prey specimens were
 broken or partially digested, they were compared to intact specimens of
 similar morphotype to confirm the trait value assigned.