Featured Image Credit: Source
By: Eva Gruber
These enigmatic and rare whales and dolphins prove that despite their large size and presence, so much of what we think we know about the oceans and our planet is yet to be discovered. Despite our long history of encounters with whales, there may still be several species that exist beneath our ability to detect them. And, even the species we know exist, from strandings and fishing, may go on living their lives without us ever seeing them in the wild.
That may be a beautiful, romantic idea, but lets hope that wherever they are, they remain safe from the dangers that humanity imposes. And that one day, we might be lucky enough to study them, come to understand them, and are then better equipped to protect them.
1. Hourglass Dolphin (Lagenorhynchus cruciger)
Inhabiting Antarctic and Subantarctic waters, the hourglass dolphin was first classified as a new species in 1824 from drawings made in the field. This makes it the only cetacean to be classified based solely on witness accounts. Despite heavy whaling in its range, only three specimens were ever recovered for study by 1960, and it is from these initial specimens that what little we know about the species exists. By 2010, six complete specimens and fourteen partial specimens contributed further bits of knowledge.
The species is rarely seen in the wild, and thus field observations are few and far between. From what has been observed, they are gregarious and occur in pods of up to 100 individuals, with an average pod size of about seven individuals. Nothing is known about their breeding and reproduction, as very few calves have been spotted. They have been seen associating with larger whale species, even bow riding off the bow waves of their larger cousins.
Like all toothed cetaceans, they use echolocation to find prey species. Recent studies revealed that they use their high-pitch clicks to find prey at twice the normal distance than other dolphin species.
2. Beaked Whales
Beaked whales, or ziphiids, include 22 species in the family Ziphiidae, and are some of the most enigmatic of cetaceans. Incredibly difficult to observe, several species are known only from strandings and have never been seen alive in the wild. Only a few have been studied in detail – there is still much to be learned about this unique cetacean family.
The beaked whales are all deep divers that spend very little time at the surface, and avoid boats – both factors which result in few sightings in the wild. They are found mostly in waters that are at least 300 m (1,000 ft) deep, and they are likely feeding on mesopelagic squid and fish. However, biological samples gained from stranded individuals or those caught by whalers has sparked a surge in knowledge of the systematics of this family – even though so little is known about their natural histories.
Beaked whales all have a beak, or rostrum, of varying length, as well as a pair of throat grooves. The ziphiids also have another unique feature – flipper pockets – which are subtle depressions in their body that reduce drag when they tuck their fins against their body.
The key distinguishing feature between different ziphiid species is the size, shape, and position of their teeth. Most species only have a single pair of teeth, which erupt only from the lower jaw of adult males. The females of this species are essentially toothless!
The erupted teeth of the males often emerge outside the jaw and can be considered tusks. Since most adult males are crisscrossed with scars, they probably use their tusks in antagonistic encounters with other males.
In 1823, the distinguished French zoologist Georges Cuvier classified an extinct whale based on a fragment of skull. However, several decades after his death it was discovered this organism was in fact, not extinct, and actually a relatively abundant species that could be found in almost all oceans worldwide.
Similar in form to other beaked whales with a stout, cigar-shaped body, and melon sloping into a stubby rostrum, or beak, individual Cuvier’s come in a variety of colors from rusty-brown to slate-gray. A tagged Cuvier’s beaked whale recently dove to a depth of 9,816 feet – a new record for marine mammals.
3. Bryde’s Whale (Balaenoptera brydei, Olsen, 1913)
Perhaps the least studied of all the great whales, the Bryde’s (pronounced “Bree-dahs”) is also the smallest of the baleen whales coming in at 50 feet long. However, despite their great size they are incredibly agile, and are even called “rocket whales” for their speedy charges through schools of their prey like krill or small fish.
Found only in tropical, subtropical, and warm temperate waters such as the Indo-Pacific, they lack a thick blubber whale like their baleen cousins. This enables them to reside comfortably in warmer waters, but also means that they cannot store energy and therefore must forage constantly. The taxonomy of this whale within its family is relatively uncertain.
There are at least two subspecies that may constitute separate species. Bryde’s whale is listed as Data Deficient by the International Union for the Conservation of Nature and Natural Resources, meaning that little information is available on its abundance and distribution.
4. Omura’s Whale (Balaenoptera omurai)
Also known as dwarf fin whales, almost nothing is known about this species. Before it was formally described it was thought to be a pygmy version of the Bryde’s whale. However, in 2003, phylogenetic studies of dead specimens proved it to be an early offshoot of rorqual species – perhaps being most closely related to blue whales.
Omura’s whales are among the smallest of rorquals, reaching a size of about 35 feet long. Very little is known about the reproduction, breeding, and diet of the species. They are thought to inhabit the western Pacific Ocean, although its exact distribution is uncertain due to the very small amount of sightings of live whales in the wild.
In 2015, researchers discovered a possibly resident population of Omura’s off the coast of Madagascar, releasing the first photos and field observations for the species. They were able to obtain biological samples which confirmed that the first live sightings were indeed of Omura’s whales.