Pesky Remoras

The Wild Dolphin Project was started by Dr. Denise Herzing back in 1985. Since then Dr. Herzing, along with her colleagues and graduate students, has put out multiple peer reviewed research papers on the behavior, acoustics, and ecology of the two species we study in the Bahamas: the Atlantic spotted and bottlenose dolphins. But over the years, she has observed behaviors that are more “rare” or are “one-offs” meaning there is not a large enough sample size in which to do a proper scientific study. However, these behaviors are very interesting and we wanted to share some of them with you. We will put out some blogs highlighting these rare behaviors and hopefully you enjoy learning about them. This will be a blog series so make sure to check back and read them all!

Rare Behavior Blog Series #2

Shake it off! Pesky Remoras

Cassie L. Volker & Denise L. Herzing

Have you ever had something stuck on you? I am sure you have and I’m guessing you simply removed it with your fingers, am I right? Well, have you ever wondered how a dolphin would remove something without fingers? 

The dolphins we observe over in the Bahamas occasionally have remoras stuck to their bodies. The whalesucker, Remora australis, is a species of remora that only attaches to cetaceans (Silva-Jr & Sazima, 2008). 

Photos of Atlantic spotted dolphins with Remoras attached. 

We have seen this remora species on both the Atlantic spotted and bottlenose dolphins of all ages in our study site. The younger animals perform aerial acrobatics (leaps) in what appears to be an attempt to dislodge the remoras. Mothers have also been observed trying to help remove the remoras from their calves by grabbing at them with their teeth. However, we have not seen any successful removals by either another dolphin or the dolphin itself, but not for a lack of trying. The dolphins try to dislodge them by a few different means: rubbing in the sand, jerking their bodies, and performing aerial acrobatics such as high leaps, belly and side smack leaps, and cartwheels (refer to our “Can anyone hear me?” Blog for what a cartwheel looks like). Occasionally, the dolphins will also jerk their bodies while performing some type of out of water leap. Keep this in mind the next time you see a dolphin leaping out of the water, they may not be doing it just for fun. These leaps burn a lot of energy and at least one reason for these jumps seems to be to try and shake the remoras from the dolphin’s body.

Here are some examples of what we have seen out in the field:

 On July 8, 2017, a male Atlantic spotted dolphin calf (Moose), was observed from the surface trying to dislodge a remora. While we watched for seven minutes, Moose performed 22 leaps that were a mix of belly and side smacks, five cartwheels, and 14 surface thrashes where he thrust his peduncle and tail from the water and then slapped them back onto the surface. 

(Watch the video clip) In this clip, you see Moose trying to get a remora off. The third leap is a cartwheel and the last is a surface thrash.

Another observation occurred on June 16, 1999, during which a juvenile female Atlantic spotted dolphin repeatedly swam to the bottom and vigorously rubbed in the sand for a few seconds before propelling herself rapidly to the surface for a leap or a cartwheel. During this encounter, it seemed that the sand rubbing was the main effort to try and dislodge the remora. 

(Watch the video clip) In this clip you can see the dolphin rubbing in the sand and leaping.

In some observations, we have also seen the spotted dolphins show signs of irritation because they can’t seem to get the remoras off. They show this irritation through bubble bursts and open mouths. For a visual representation of the irritation and underwater behavior leading up to a leap, check out this video clip.

(Watch the video clip)

Currently, we do not know if the remoras help or hinder the dolphins. From the aerial behavior, we speculate the remoras irritate the dolphins.  Remoras are most commonly seen on the dolphins when the dolphins have some kind of skin issue. 

However, at this time we do not know if the skin issues are caused by the remoras or if the remoras are aiding in the healing process. Silva-Jr & Sazima (2008) mentioned that whalesuckers, seen on spinner dolphins (Stenella longirostris) in the Fernando de Noronha Archipelago, were seen cleaning off some fungal infected skin, but they were also a nuisance depending on where they were attached on the dolphin’s body. 

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Reference: 

Silva-Jr, J. M., & Sazima, I. (2008). Whalesuckers on spinner dolphins: an underwater view. Marine Biodiversity Records, 1. https://doi.org/10.1017/S1755267206002016