A sperm whale that stranded in the Canary Islands in 2023 died from a large intestinal blockage caused by ambergris, a substance long associated with the perfume industry. The case is one of several recent strandings that have drawn attention to the health threats facing these animals, including parasitic infections and internal injuries that are only visible during necropsies.

Sperm whales are the largest toothed predators on the planet, with males reaching lengths of around 18 meters. Their lives center on deep diving to hunt giant squid and other prey in total darkness. A normal feeding dive takes them between 600 and 1,000 meters, and tagged individuals have been recorded going past 2,000 meters. To tolerate the pressure at those depths, a sperm whale shuts down nearly every non-essential body function while diving. Digestion stops, blood pulls away from the skin and limbs and redirects to the heart and brain, and a large oil-filled organ in the head helps with buoyancy and focused sound for hunting.

Many sperm whales carry scars from squid hooks and suckers, evidence of battles with prey far larger than themselves. Their teeth, functional only on the lower jaw, are often worn down from decades of grasping struggling prey in darkness. But the inside of a whale’s body can hold its own set of challenges, many of which are only discovered after death.

Before modern science, whalers occasionally found waxy, foul-smelling lumps inside sperm whale intestines. Once dried and aged, this substance, ambergris, developed a pleasant scent and was used for centuries in perfume. It is now known to form when the whale’s body produces a protective coating around sharp, indigestible squid beaks and other fragments that accumulate in the digestive tract.

In May 2023, a 13-meter male sperm whale washed up dead at Playa Los Nogales on the island of La Palma in Spain’s Canary Islands. A necropsy carried out within 48 hours found a solid mass about 50 centimeters across and weighing 9.5 kilograms blocking the whale’s lower colon. This was ambergris, hardened waste material containing squid beaks and fish lenses. A 5-centimeter metal fishing hook was found nearby in the stomach contents. Lab tests identified three types of intestinal bacteria, and researchers concluded the blockage had led to a fatal blood infection that caused the animal’s death.

The case demonstrated how much can go wrong inside a sperm whale’s digestive tract without any visible external injury. It also fit into a broader pattern of findings from other stranding events.

Squid beaks are the main stomach content of sperm whales, since they are indigestible and can clump into dense masses over time. Modern debris adds a separate risk. In 2020, researchers at Spain’s El Valle Wildlife Rescue Center found 64 pounds of plastic packed inside a young sperm whale stranded in the south of the country, which they believed contributed to its death. In 2018, a stranded sperm whale in Spain carried a roughly 220-pound mass made almost entirely of tangled ropes, fishing nets, and plastic debris. Similar cases have been reported around the world, often involving food unable to pass through the digestive tract. Marine biologists now regard plastic ingestion as one of the clearest and most preventable threats facing the species.

Parasites add another layer of complexity. Deep inside the reproductive tissue of pregnant sperm whales lives Placentonema gigantissima, a roundworm first described by Soviet researcher A. G. Gubanov in 1951. It holds the Guinness World Record as the longest nematode ever documented, with specimens reaching roughly 8 meters and several centimeters thick, coiled inside the placenta rather than the gut. Because it lives only in placental tissue, researchers encounter it only while examining pregnant females, making each finding rare.

A separate tapeworm, Tetragonoporus calyptocephalus, lives in the intestines of sperm whales and other large whales. Estimates place its maximum length near 30 meters, with some older reports suggesting specimens closer to 40 meters. Fully intact specimens are rarely recovered, as the worm’s body is fragile and long. It grows segment by segment, attaching to the intestinal wall while new segments form behind, each carrying its own reproductive organs. Some individual worms have been described with as many as 45,000 segments.

In 2025, researchers studying stranding records found three previously unknown types of Helicobacter bacteria in the stomachs of stranded pygmy sperm whales. The four infected whales in the study all showed digestive damage, including inflammation, ulcers, scarring, and parasite infestations, though scientists have not confirmed the bacteria as a direct cause of death. Pygmy sperm whales are difficult to study because they spend most of their lives far from shore, travel in small groups, and rarely surface for long. Weighing up to 1,000 pounds and rarely growing past a few meters, they share the deep-diving habits and squid-heavy diets of their larger relatives, exposing them to similar hazards.

A young pygmy sperm whale found in difficulty near Utila, Honduras in August 2025 was found during a necropsy to have an 11-inch plastic bag in its stomach, along with a parasite infestation that likely contributed to its death.

The discovery of new bacteria in pygmy sperm whales has prompted some researchers to re-examine older stranding cases. If bacteria this significant went undetected for years, some scientists now ask whether older deaths attributed only to plastic, ship strikes, or unclear causes might have involved unseen infections. This does not overturn confirmed findings on plastic and fishing gear, but it does mean preserved tissue samples from past strandings are being examined with modern genetic tools that did not exist when the whales were first studied.

These re-examinations are slow and rarely produce a single dramatic answer. They tend to reveal that a death once blamed on one cause may have involved several factors. Genetic sequencing now allows researchers to identify bacteria from tiny preserved samples collected decades ago, meaning frozen specimen archives could hold information nobody had previously considered.

Several basic questions remain unanswered. No one knows how common Tetragonoporus calyptocephalus infections are across the global sperm whale population, since recovering one intact depends on luck and timing during a necropsy. It is not confirmed whether the newly found Helicobacter bacteria kill their host directly, weaken its immune system, or simply coexist with other health problems. Researchers also lack a clear picture of how often ambergris blockages like the one in La Palma occur at sea, since most cases surface only when an already dead whale washes ashore. Whales that die from internal causes in open ocean often sink or are scavenged before anyone can examine them, meaning documented cases may represent only a small fraction of the real pattern. Scientists acknowledge that stranded animals are not necessarily representative of the wider population, as a whale dying at sea leaves no record.

The overall picture of the sperm whale as a hardy deep-diving predator remains unchanged. What has shifted is confidence in how much scientists know about what happens inside these animals once they die. A worm longer than a city bus, bacteria previously unclassified, and a blockage formed from the whale’s own defenses have all been found inside bodies studied for decades. Each new necropsy continues to show that the sperm whale’s most difficult challenges are not only met in the deep against squid. Some of its most unusual survival stories are playing out quietly inside its own body, and researchers are still working to understand what has been hidden there all along.