Our “Species of the Week” series highlights the flagship species of each of the 844 unique ecoregions contained within Earth’s bioregions.
In the muddy waters of the Amazon river, a pink dorsal fin stands out as it weaves between submerged tree roots along the banks. Botos, or Amazon river dolphins, are a distinct species in this jungle landscape — their bright color due to their capillaries being near the surface of their skin. Much like their saltwater cousins in temperament, they swim and play along with the boats of local fishermen and researchers alike. However, pink river dolphins are a bit more farcical looking with a lumpy head, beady eyes, and long snout that seems to be grinning. These are the largest of the five freshwater species of dolphin, growing up to nine feet long and weighing over 400 pounds.
Breeding and birthing take place between May and July, aligning with peak water levels. As floodwaters begin to decrease, the density of prey increases due to the loss of habitat. This allows easy nourishment for the high energy demands of giving birth and nursing. Males begin the season by offering a gift to a female. Branches, leaves, or balls of hardened clay are presented and if accepted, the male begins foreplay by nibbling the fins of the female. The compilation is frequent and multiple positions have been observed. Gestation is estimated to be around eleven months and lactation is over a year as the mother cares for her calf. Born dark gray, juveniles become lighter with age and are thought to become independent within two to three years.
Although they can see out of their eyes, Amazon river dolphins primarily use echolocation to navigate the dark waters. The large melon on their head serves as a lens helping them focus their low amplified sounds. They can emit 30-80 clicks per second when locating prey. Their diet consists of at least 53 different species of fish and their narrow jaw contains 25 to 28 pairs of teeth which allow them to crack shells of turtles and freshwater crabs. Whistling tones are also used to communicate with one another. Amazon river dolphins are commonly observed in pairs or groups of three, but pods as large as 37 have been spotted.
While poaching poses a major threat, Amazon river dolphins are endangered due to loss of habitat and pollution, often found entangled in abandoned fishing lines. All caused by outside influence in the region. In traditional Amazon River folklore, botos are known as shapeshifters called encantados. Turning into beautiful men or women at night, they seduce local villagers to the Underworld of Encante. Legend forbids the killing, eating, or even gazing into the eyes of river dolphins for fear of bad luck. For abundant fishing or location of the sacred Amazonian manatee though, the myth states one must make peace with the “guardians of the river.”