Subaerial naticid gastropod drilling predation by Natica tigrina on the intertidal molluscan community of Chandipur, Eastern Coast of India

Highlights

• Reports of subaerial naticid foraging are common, but lack proper quantification.

• Detailed analyses of subaerial hunting by Natica tigrina have been done from India.

• N. tigrina opportunistically attacked both epi- and infaunal prey.

• Intensity of drilling predation (DF) on the molluscan assemblage was high (25.7%).

• Strong site and size stereotypy indicated efficient predation by N. tigrina.

Abstract

Chandipur intertidal flat in eastern coast of India is a killing field. The vast stretch of intertidal habitat opens up during the low tide, and is monopolized by a single naticid species which preys extensively on intertidal taxa. The predator, Natica tigrina, wades through the soft sediments and ambushes on epi- or infaunal prey.

There were reports on naticid subaerial hunting, where the workers made vivid observations, but only in few instances quantified different aspects of predation. Detailed quantitative analyses of the present study revealed that N. tigrina attacks opportunistically on all infaunal and epifaunal intertidal bivalve and gastropod prey taxa. Drilling frequencies ranged from 9.70% to 67.67% with no apparent relation with relative abundances of the taxa. High drilling frequency on conspecific predation perhaps suggested elimination of the potential competitor as well as a profitable prey. Behavioral data of predation, i.e., stereotypy of site and size of drillholes on prey shells and low prey effectiveness indicated that the predator was highly efficient.

Introduction

Gastropod drilling predation by the members of the family Naticidae and Muricidae is one of the major subjects of interest of both ecologists and paleocologists in recent decades (see Kelley and Hansen, 2003 for review; Dietl and Alexander, 1995, Dietl and Alexander, 2000, Kelley and Hansen, 2007, Klompmaker, 2011, Bardhan et al., 2012, Ottens et al., 2012, Paul et al., 2013, Visaggi et al., 2013, Hattori et al., 2014, Mondal et al., 2014, Das et al., 2014, Mallick et al., 2014). Among many groups of drilling gastropod predators, muricid gastropods generally drill their prey epifaunally, whereas naticid gastropods attack both infaunal and epifaunal prey and always drill the victim within the sediments (Sohl, 1969, Carriker, 1981, Mondal and Harries, 2013). In addition, naticid gastropods have been reported to drill their prey in shallow to deep water (Ziegelmeier, 1954, Carriker, 1981, Sawyer and Zuschin, 2010, Visaggi et al., 2013). However, there are few cases where naticid gastropods invaded exposed intertidal areas and preyed upon molluscan species (Dietl, 2002 and references therein). For example, Gonor (1965) observed predation by Natica unifasciata Lamarck, 1822 on the intertidal flats of the Pacific coast of Costa Rica. Similarly, Hughes (1985) demonstrated the foraging behavior of the same predator species from the sandy beach of Veracruz and mud flat in the bay of Panama. Savazzi and Reyment (1989) documented the subaerial hunting behavior of Natica gualteriana Récluz, 1844 from the intertidal sand bars in Bantayan Island, Philippines. In comparison, although there are many studies on direct field observations of their predatory behaviors (Ziegelmeier, 1954, Ansell, 1960, Gonor, 1965; see also Mondal et al., 2014 for other references), only few studies quantified the intensities of naticid predation in the intertidal regions (Savazzi and Reyment, 1989, Sawyer and Zuschin, 2010, Zuschin and Ebner, 2015). Detailed field observation of intertidal naticid predation, along with quantification of several aspects of this interaction, is severely lacking.

Here, we quantified several aspects of predation by Natica tigrina (Röding, 1798) in the intertidal region of Chandipur, eastern coast of India. N. tigrina has been designated as Notocochlis tigrina in other parts of the world. The workers in India believe that N. tigrina is a distinct species in the Indian subcontinent and is widely used by the recent workers (Mondal et al., 2010, Chattopadhyay et al., 2013, Paul et al., 2013, Das et al., 2014). Moreover, this Indian species is a valid species in the GBIF database. We therefore retained the name of this species as N. tigrina in this paper.

Drilling frequency (DF) was compared with prey availability, prey life mode, conspecific competition, and cannibalism to test the following hypotheses: (1) DF is positively correlated with prey abundance because prey abundances is a proxy for encounter frequency (Leighton, 2002); (2) being an infaunal predator, N. tigrina would target mostly the infaunal prey; (3) the predator ranks their prey based on the net energy return, so that the highest-ranked prey is likely to have the highest DF and vice versa; (4) DF varies with prey size with larger sizes being less frequently drilled, because maneuverability of larger individuals is difficult (Dudley and Vermeij, 1978, Allmon et al., 1990, Tull and Böhning-Gaese, 1993, Paul et al., 2013; see also Leighton, 2001 for detailed discussion); (4) drilling is site-specific; (5) prey with active defenses are less frequently drilled, and have high rate of failure (i.e., more incomplete attacks); and (6) DF in the intertidal region of India is comparable with the previously published data (Sawyer and Zuschin, 2010, Sawyer and Zuschin, 2011, Zuschin and Ebner, 2015).