Hurricanes generate colossal waves, storm surges, and torrential rains. For coastal marine mammals like the Bottlenose dolphin, these powerful tropical cyclones pose a challenge to survival. Dolphins employ specific adaptations and behaviors to navigate these events.
Sensing the Approaching Storm
Dolphins possess highly developed sensory systems that allow them to detect a hurricane’s approach. Their bodies are sensitive to the rapid drop in barometric pressure that precedes a major storm system. This change in atmospheric pressure acts as an early warning signal, prompting a shift in behavior.
The initial rain bands associated with a hurricane can cause a measurable decrease in ocean salinity and temperature near the coast. Dolphins perceive these shifts in water chemistry, providing cues that a powerful weather event is imminent. Furthermore, their acute hearing allows them to detect the low-frequency sounds and vibrations generated by the distant, intensifying storm. This early detection allows dolphin pods to alter their activities, often becoming more cohesive and cautious before the weather deteriorates.
Seeking Refuge During Peak Conditions
When a hurricane reaches its maximum intensity, dolphins engage in two primary strategies to seek refuge from the most destructive surface turbulence. For populations that inhabit offshore waters, the main survival strategy is to move into deeper water. By swimming to depths of 10 to 20 meters or more, dolphins can avoid the most dangerous surface waves and strong currents, which are most violent near the air-water interface.
The deep-water movement minimizes the risk of being swept away or injured by debris. Staying deep allows them to ride out the storm in calmer conditions, surfacing only briefly to breathe. For coastal populations that cannot access deep oceanic waters, the strategy shifts to finding natural, sheltered areas along the coastline.
Coastal dolphins often retreat to protected inlets, deep shipping channels, or estuaries that offer a buffer from the worst winds and storm surge. This coastal refuge is a calculated risk, however, as it exposes them to the immediate effects of storm surge and debris. Following Hurricane Harvey, dolphins in Galveston Bay moved from shallow open areas to deep channels. This demonstrates their ability to prioritize areas offering physical shelter and tolerable water conditions during the storm’s peak.
Post-Storm Challenges and Recovery
The immediate aftermath of a hurricane presents a new array of dangers for dolphins, often involving displacement and physiological stress. Massive storm surges can push coastal dolphins far inland, stranding them in low-lying areas like flooded fields or landlocked ponds once the water recedes. These displaced animals are then trapped, sometimes for weeks or months, unable to return to their natural habitat without specialized human intervention.
A major threat is the sudden and prolonged exposure to massive freshwater runoff from the land, leading to what is known as freshwater shock. Dolphins can tolerate low salinity briefly, but extended exposure causes severe skin lesions that can cover large portions of their bodies. These lesions are comparable to third-degree burns and allow for the disruption of electrolytes in the bloodstream, which can lead to organ failure and secondary infections.
The coastal environment itself is severely compromised, presenting challenges to feeding and general health. Storm-stirred sediment and massive runoff drastically reduce underwater visibility, making it difficult for dolphins to hunt using echolocation.
Furthermore, the water is often contaminated with pathogens, toxic chemicals, and storm debris, posing a serious health risk and potential for physical injury. The long-term survival of the pod depends on a complex recovery phase, including the availability of prey species and the ability of surviving dolphins to restructure their social groups.