| Primary search (Phase 1, Fig. 2) |
Active-scanning (Fig. 2a and video S1) |
Swimming just above the bottom (1-20 cm) using undulatory movements of the pectoral fins while searching for prey. The stingray generates a wave at the margin of the pectoral fins that begins at the level of the eye and propagates posteriorly. While scanning, the individual’s entire body follows the bottom relief. |
| Glide-scanning (Fig. 2b and video S2) |
Gliding through the water just above the bottom (1-20 cm), keeping the pectoral fins motionless while searching for prey. The glide-scanning can be performed due to the inertia of a previous “active-scanning” or may be due to water flow. While scanning, the individual’s entire body follows the bottom relief. |
| Turn-back (Fig. 2c and video S3) |
An abrupt turning maneuver during “active-scanning” or “glide-scanning”. Scanning later continues in the opposite direction. |
| Reverse (Fig. 2d and video S4) |
Swimming backwards. The stingray shifts the direction of the undulatory movements of its pectoral fins causing the individual to swim backwards while close to (but not touching) the bottom. It could happen with some rotation of the body on the dorsal-ventral axis. |
| Rotation (Fig. 2e and video S5) |
Rotating on the dorsal-ventral axis close to the bottom, yet without touching it. The rotation may be in either direction and take different forms: (i) only one pectoral fin is used in the normal direction of the undulatory movement; (ii) only one pectoral fin is used in the opposite direction of normal undulatory movement; (iii) both pectoral fins are used simultaneously, one in the normal direction and the other in the opposite direction; (iv) the tail is used in association with other movements. |
| Settled upon the bottom (Phase 2, Fig. 3) |
Smooth-landing (Fig. 3a and videos S3 and S6) |
Stopping and settling smoothly with the margins of the pectoral fins margins touching the bottom. This probably occurs once prey is detected. |
| Rough-landing (Fig. 3b and video S7) |
Stopping suddenly and settling abruptly with the margin of the pectoral fins touching the bottom. This probably occurs once prey is detected. |
| Secondary search on the bottom (Phase 3, Fig. 4) |
Reverse on the bottom (Fig. 4a and video S8) |
Moving backwards while touching the bottom. The individual pushes itself against the bottom with its pectoral fins in order to move backwards with its body still facing forward and/or shifts the direction of the undulatory movement of the pectoral fins. Pectoral fin movements may be discrete or obvious. |
| Rotation on the bottom (Fig. 4b and video S9). |
Rotating on the dorsal-ventral axis while touching the bottom. The rotation can be performed in either direction and may take different forms: (i) the stingray pushes itself against the bottom with its pectoral fins; (ii) only one pectoral fin is used in the normal direction of the undulatory movement; (iii) only one pectoral fin is used in the opposite direction of normal undulatory movement; (iv) the stingray pushes itself against the bottom and both pectoral fins are used simultaneously, one in the normal direction and the other in the opposite direction; (v) the tail may also be used in association with other movements. |
| Short forward displacement (Fig. 4c and video S10). |
Propelling itself forward along a very short distance and then settling back on the bottom. During this behavior, the individual pushes itself against the bottom with its pectoral fins and/or performs the normal undulatory pectoral fin movement to move forward for a short distance, as if in a “jump”. |
| Hit the bottom (Fig. 4d and video S11) |
Propelling itself upright and settling back on the bottom. In this behavior, the individual pushes itself against the bottom with the pectoral fins, displaying vertical displacement. The stingray may detach the whole disc or part of it from the floor. |
| Digging (Fig. 4e and video S12). |
Excavating the substrate. The individual lifts and then lowers its snout. It may also undulate the margins of the pectoral fins. During this behavior, a large plume of sand is usually observed around the stingray. |
| Jetting water (Fig. 4f and videos S13 and S14). |
Jetting water into the substrate. The water is expelled from the mouth and possibly from the gill slits as well. A plume of sediment is blown forward near the snout. |
| Passive inspection (Fig. 4g and video S15) |
Keeping still for a while (completely motionless). The individual’s entire body remains on the bottom over a potential prey item. This normally lasts a few seconds, but may occasionally last for minutes. |
| Active inspection (Fig. 4h and video S16). |
Keeping still for a while with its disc in a convex shape. The individual keeps the pectoral fins firmly pressed against the bottom, with the scapular region arched upright over a potential prey item. During this behavior, the tail of the stingray is raised in an angle of about 30°. The stingray may adjust the margin of the pectoral fins. This behavior normally lasts a few seconds, but may occasionally last for minutes. |
| Suction (Phase 4, Fig. 5) |
Spiracular suction (Fig. 5a and video S13). |
Taking water and sediment into the mouth while keeping still. The stingray quickly opens and closes its spiracle and flushes sediment through it. This behavior may occur during “passive inspection”, probably to ingest a prey item. |
| Corporeal-spiracular suction (Fig. 5b and video S10). |
Taking water and sediment into the mouth while keeping still with the disc in a convex shape. The stingray quickly opens and closes its spiracle and flushes sediment through it while lifting and pressing the entire disc against the bottom. This behavior may occur during “active inspection”, probably to ingest a prey item. |
| Final Phase (Phase 5, Fig. 6) |
Active take-off (Fig. 6a). |
Detaching from the bottom by pushing against it with the pectoral fins. The stingray lifts its snout while pushing against the bottom and then starts to swim. |
| Drift take-off (Fig. 6b). |
Detaching from the bottom simply by letting itself drift with the water flow. |
| Rest (Fig. 6c). |
Settling down and keeping still for a long period, completely motionless, on the bottom. |
| Bury (Fig. 6d). |
Burying itself into the substrate. |
Unravelling the foraging behavior of the southern stingray, Hypanus americanus (Myliobatiformes: Dasyatidae) in a Southwestern Atlantic MPA
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