Dolphins are widely admired for their intelligence and playful demeanor. While often seen as symbols of grace, it’s important to recognize the full scope of their behavior. Dolphins can pose risks, shifting the perception from benign to potentially dangerous.
Aggressive Encounters
Dolphins can exhibit aggressive behaviors due to factors like territorial defense, protecting their young, or sexual frustration. These actions aren’t always malicious, but can result from feeling threatened or agitated by human presence. Documented cases show dolphins intentionally biting, ramming, or pushing.
In Japan’s Fukui prefecture, a male Indo-Pacific bottlenose dolphin has been responsible for numerous attacks, causing injuries from minor bites to broken bones. Researchers suggest its aggression may stem from loneliness or misdirected mating behaviors, as male dolphins express sociality and dominance through physical interactions like biting and mounting. Though rare, such encounters can lead to severe harm.
Dolphins habituated to human feeding can become aggressive, acting pushy or forceful when food isn’t provided. Behaviors like tail slapping, jaw claps, or body slamming establish dominance within dolphin social hierarchies. These can be directed towards humans if a threat or disruption is perceived. Thus, even typical dolphin behaviors can become dangerous when humans are involved.
Unintentional Injuries
Dolphins can cause significant harm due to their size, strength, and speed, even without aggressive intent. An adult bottlenose dolphin weighs 300 to 1,400 pounds and measures 6 to 12 feet long. They can swim up to 22 miles per hour, with some species reaching 37 mph. Their powerful physicality means accidental contact can lead to serious injury.
Collisions or being caught in a dolphin’s powerful movements are risks. A playful but forceful nudge or accidental tail slap can result in broken bones, internal injuries, or drowning. One woman suffered blunt force trauma after landing on a dolphin’s dorsal fin during a “swim with dolphins” experience, describing the impact as a car accident. These incidents are not driven by malice, but by the sheer force generated during their natural behaviors. Even when a dolphin intends a “gentle” interaction, its sharp teeth can inflict wounds.
Health Risks
Direct contact with dolphins poses health risks through zoonotic disease transmission. These illnesses spread between animals and humans. Brucella species, bacteria causing brucellosis, have been found in dolphins and can transmit to humans via contact with infected animals or their bodily fluids. Human brucellosis can cause flu-like illness, chronic arthritis, and neurological issues. Recent Hawaiian cases show stranded dolphins testing positive for Brucella ceti, raising concerns about a new strain.
Mycobacterium marinum is another concern, causing skin infections in humans, often called “fish tank granuloma.” Infection can occur if contaminated water or direct contact with an infected dolphin introduces bacteria through open wounds. Found in salt and fresh waters, Mycobacterium marinum can naturally infect aquatic mammals like dolphins. While viruses like morbillivirus and herpesvirus are found in dolphins, the dolphin morbillivirus type is not known to infect humans.