Do shortfin mako Isurus oxyrinchus hunt dolphins actively?

Abstract

Direct evidence of shark predation on cetaceans is scarce, making it difficult to differentiate between stomach contents that have been scavenged and actively hunted. This study reports the presence of dolphin (Tursiops aduncus and Stenella clymene) remains in the stomachs of three large shortfin makos Isurus oxyrinchus. Detailed analysis suggested active predation in at least one case, supported by premortem bite marks. This observation represents the first record of S. clymene in the diet of a shortfin mako. These findings highlight the opportunistic nature of shortfin mako, which may prey on juvenile dolphins under certain ecological conditions, providing new insights into their feeding behaviour and trophic ecology.

Sharks are assumed to be important predators of marine mammals, but direct evidence of this type of interaction is scarce. Although studies have reported cetacean species inside the stomachs of different shark species, it is often unclear if this is the result of direct predation of free‐swimming animals or scavenging (Heithaus, 2001).

Species such as the white shark Carcharodon carcharias (Linnaeus, 1758), the tiger shark Galeocerdo cuvier (Péron & Lesueur, 1822), the bull shark Carcharhinus leucas (Valenciennes, 1839) and the dusky shark Carcharhinus obscurus (Lesueur, 1818) frequently consume cetaceans, specifically dolphins (Cockcroft et al., 1989; Heithaus, 2001). Although the shortfin mako Isurus oxyrinchus Rafinesque, 1810, is not in that list, it is one of the fastest sharks in the world (Diez et al., 2015) and is potentially capable of hunting prey with high swimming capacity, such as dolphins. Cetaceans and specifically dolphins were found in shortfin mako stomachs previously (e.g. Klarian et al., 2018; Mucientes & Saborido‐Rey, 2008), but there is little evidence that they actively prey on dolphins (Monteiro et al., 2006; Okamura et al., 2024; Silva Jr et al., 2007). Specifically, the feeding habits of the shortfin mako vary based on geographic location, ocean productivity and prey availability (Calle‐Morán et al., 2023; Mucientes & Saborido‐Rey, 2008).

Here, we show the stomach contents of three large adult shortfin makos (>2 m total length) from the South Pacific and North Atlantic oceans, confirming the consumption of juveniles of two different dolphin species. The Indo‐Pacific bottlenose dolphin T. aduncus (Ehrenberg, 1832 [1833]) was recorded twice (Figure 1a,b), in two different sharks from the South Pacific Ocean (19 and 23 January 2005, 33.08° S 135.03° W and 30.32° S 134.92° W, respectively). In both cases the dolphins were calves and found in several large, partially digested pieces. The Clymene dolphin Stenella clymene (Grey, 1850) (Figure 1c) was found in the stomach of a shortfin mako captured south of the Cape Verde islands (30 April 2018, 5.60° N 18.13° W); the specimen was a large immature individual. This is the first report of this dolphin species from the stomach contents of a shortfin mako.

FIGURE 1.

(a, b) Tursiops aduncus remains from the stomach of two shortfin mako individuals from the South Pacific Ocean. Note the difference in size between the two individuals (for reference, the yellow knife is 37 cm long). (c) Stenella clymene remains from the stomach of a shortfin mako found in the North Atlantic Ocean. Note the multiple scars on the skin mainly in the top of the head; red circles represent potential defence scars and yellow circles muscular activity response (for reference, the syringe is 20 cm long).

Detailed examination of the dolphin remains suggests that the S. clymene may have been actively preyed upon (Bornatowski et al., 2012). The head shows evidence of shark bites, characterized by wounds that exhibit indications of being premortem. The wounds have well‐defined edges and partial tissue loss, including one case with tearing, suggesting a possible attempt to escape or defend (highlighted in red circles, Figure 1c). These wounds are accompanied by fight scars or abrasions near the main injuries, which could indicate muscular activity in response to the attack (highlighted with yellow circles, Figure 1c; Nicholls et al., 2023). The specimen of S. clymene was a subadult, which may have offered greater resistance to the capture. In the case of T. aduncus, they were neonate specimens (of different sizes) with less ability to escape, which could have facilitated their capture if adults were not nearby.

In conclusion, although dolphins are not their primary prey, shortfin mako sharks may occasionally hunt juvenile dolphins. In these cases, the energy spent on capturing dolphins is justified by the high nutritional value they provide.

AUTHOR CONTRIBUTIONS

All authors contributed to the conceptualization, design, methodology, and writing of the study. Gonzalo Mucientes conducted field observations and prepared the images.

CONFLICT OF INTEREST STATEMENT

The authors declare no competing interests.

SAMPLING AND FIELD STUDIES

The authors have obtained all necessary permits for observational field studies from the Spanish competent authorities. The study is compliant with CBD and Nagoya protocols.

Mucientes, G. , Vilas‐Arrondo, N. , & Villegas‐Ríos, D. (2025). Do shortfin mako Isurus oxyrinchus hunt dolphins actively? Journal of Fish Biology, 107(4), 1433–1435. 10.1111/jfb.70113

DATA AVAILABILITY STATEMENT

Data sharing is not applicable as no new data were generated, or the article describes entirely theoretical research.