Unveiling the Electrifying Secrets of Hilton Head’s Bottlenose Dolphins

In a remarkable breakthrough, researchers at the Nuremberg Zoo in Germany have uncovered a previously unknown sensory ability in bottlenose dolphins: electroreception. This groundbreaking revelation not only establishes a connection between dolphins and other electroreceptive animals but also enhances our comprehension of how these fascinating creatures engage with their aquatic surroundings. What’s even more intriguing is the potential impact of this newfound sixth sense on the dolphins around Hilton Head Island.

Electroreception and its Implications for Hilton Head’s Dolphins

Electroreception, the ability to detect weak electric fields, is typically associated with aquatic or semi-aquatic species. While extensively studied in marine biology, particularly in weakly electric fishes and certain amphibians, this sensory skill has now been identified in bottlenose dolphins, challenging preconceived notions and expanding our insights into marine sensory biology.

Picture a dolphin navigating the dark sediment rich waters along Hilton Head, relying not on light but on faint electrical signals from hidden prey to illuminate its path. This newfound ability could revolutionize our understanding of their foraging strategies, especially in challenging environments around Hilton Head’s unique marine ecosystem. Moreover, this sixth sense may extend beyond foraging, playing a possible role in navigation and communication within the vast expanse of the ocean that surrounds Hilton Head.

The Electrifying Research Journey

The journey into this electrifying discovery began with an intriguing observation about bottlenose dolphin calves, born with whisker-like structures along their snouts. These structures, reminiscent of those in sharks that detect electric fields, prompted scientists to conduct experiments to determine if adult dolphins retained a similar electrosensory capability after the whiskers fell out.

Two female bottlenose dolphins, Dolly and Donna, were the stars of the study. Under the guidance of marine biologists Tim Hüttner and Guido Dehnhard, the research team designed a sophisticated experiment to assess the dolphins’ ability to detect electric fields. The setup, in a controlled pool environment, exposed the dolphins to both direct current (DC) and alternating current (AC) electric fields.

The experimental design showcased scientific precision and patience. The trained dolphins actively participated, facing varying strengths of electric fields. Researchers systematically reduced field intensities to pinpoint the exact threshold of the dolphins’ electroreceptive abilities, ensuring the accuracy and reliability of the results.

Sensitivity Beyond Expectation

The findings were truly remarkable. Dolly and Donna exhibited acute sensitivity to electric fields, detecting strengths as low as 5.5 and 2.4 microvolts per centimeter for DC fields, respectively. Their ability to sense AC fields, varying with frequency, emphasized their remarkable electroreceptive capabilities.

The study delved further into whether dolphins could detect pulsating electric fields, similar to those generated by fish gill movements. Astonishingly, both Donna and Dolly demonstrated this ability, although their sensitivity to oscillating fields was not as acute as to static fields. Donna, notably more sensitive, could detect the slowest pulsating field at 11.7 microvolts per centimeter.

A pod foraging along Haig Point. Are they using visual identification, echolocation or electro-sensory to trap prey?

Implications for Hilton Head’s Marine Biology and Conservation

This sensory prowess of dolphins opens a new chapter in understanding their interaction with the marine environment around Hilton Head. Electroreception could prove crucial in benthic foraging, aiding dolphins in locating food along the seafloor, especially in conditions where visibility is poor, and echolocation is less effective, such as in the murky, sediment-laden waters near Hilton Head.

Additionally, the researchers propose that dolphins might use their electrosensation in conjunction with the Earth’s magnetic field for navigation, suggesting a global-scale application of this sensory ability that may also influence the behavior of dolphins in the waters around Hilton Head.

The discovery of electroreception in Hilton Head’s dolphins holds wide-ranging implications, both scientifically and ecologically. It challenges existing paradigms in marine sensory biology, suggesting that these animals have evolved complex and nuanced ways to survive and thrive underwater. The study underscores the importance of conservation efforts, emphasizing that understanding these intricate adaptations is crucial for protecting these species and their ecosystems in the waters around Hilton Head.

Future studies could provide insights into how dolphins employ this sense in their daily lives. These studies could encompass hunting, foraging, social interactions, and navigation, opening up possibilities as vast as the waters themselves that surround Hilton Head. To learn more about our amazing dolphin population, come out for a private tour! Up to 6 passengers we’ll find dolphins throughout and learn about them.

The Vanishing Mile Isle: What’s Happening in 2023?

The Vanishing Mile Isle is a mile long sandbar exposed at low tide. Officially named Grenadier Shoal on nautical charts, it has been a popular excursion near Daufuskie Island. Tour companies on Hilton Head have taken guests to explore the bar for years. Treasures found include sand dollars, sea shells and shark teeth among the tidal pools

The key to a successful visit lies in catching the right low tide, a phenomenon that varies daily due to the gravitational pull of the sun and moon. Tides around a quarter moon phase result in weak tidal exchanges, while full or new moons bring larger tidal variances.

Understanding a Tide Chart

Tide charts use “Chart Datum,” which includes terms like “mean high water” and “mean lower low water,” representing average high and low tide depths over a 19-year period. Concerning low tide, the focus is on the “mean lower low water” average. Zero on tide charts signifies the average for these low tides.

Normally, any low tide exceeding +0.50 ft above the average allowed for exploration of the Vanishing Mile Isle. During new or full moons, negative tides exceeding 1.5 feet below average would reveal a vast surface area to explore.

2023: A Year of Changes

Spring 2023 brought unseasonably cool weather to Hilton Head, with strong northeastern winds prevailing throughout April and May. These winds not only kept Hilton Head cool but also had a dramatic impact on the Vanishing Mile Isle. The persistent northeastern winds created strong surf, pounding the shoals for weeks, displacing sand, and smoothing out the sandbar. By the time these winds subsided, the island had lost over a foot of its height. What was once visible with a low +0.50 feet, now required a negative tide of -0.50 feet to be seen.

As summer progressed, traditional southern winds helped rebuild the Vanishing Mile Isle. Tybee Island sits directly south of the sandbar, and helps prevent heavy surf buildup, allowing the sand to gradually stack up and the sandbar to return. While not a complete rebuild, by August, almost 6 inches of lost height had been regained.

However, September brought more northeastern winds, including the effects of Hurricane Idalia, Hurricane Lee, and Tropical Storm Ophelia. These winds further flattened the island, making the situation worse than before.

The Vanishing Island has Vanished!

Even a negative tide of -0.50 feet is insufficient to reveal the sandbar. As October approaches, forecasts continue to predict northeast winds, exacerbating the issue. Consequently, Cross Island Cruises has temporarily suspended its beachcombing excursions to the Vanishing Mile Isle until the end of the year, or when conditions improve. While we aim to provide exceptional experiences, the sandbar currently falls short of expectations. Any interest in this tour should contact us directly for alternative ideas of exploring our waters.

Other companies may continue to operate the tour as usual, but it’s advisable to check with them to ensure they are aware of the loss of exposure or if they have alternative plans in mind. Nobody wants to embark on a 2 to 3-hour boat ride with specific expectations, only to find nothing at the destination.

sandbar exposure level 10/28/23, -.21 MLLW

*****OCTOBER 28 UPDATE******

We have seen an improvement in the height of Vanishing Mile Isle. Tours this weekend with a negative low tide level of -.21 feet did present acceptable areas of exploration. We will continue to operate this tour on a limited basis. If interested in taking a tour, feel free contact us to inquire about certain days of availability.

Strand Feeding Dolphins of Hilton Head Island

While taking a dolphin tour on Hilton Head Island, there are many opportunities to view wildlife in all its beauty and wonder. Nothing, however, compares with getting an opportunity to witness these beautiful creatures strand feeding along the shores of our waters.

What is Strand Feeding?

Dolphins are well known for their complex social behavior and intelligence. While taking a dolphin tour on Hilton Head, both these traits can be seen exhibited through an amazing hunting technique known as “strand feeding.” It involves herding fish up onto a mudflat in the shallow waters around low tide. Working together to corral the fish into tight groups, the dolphins then turn into the school of fish, creating a massive force of water, pushing themselves and the fish onto the mudflat. They then use their rostrum (beak) to pluck individuals out of the group and swallow them whole. Once they have eaten the fish stranded on the shoreline, they then wiggle themselves back into the water, regroup and do it again.

The few. The proud. The strand feeders.

While its estimated we have a couple hundred resident dolphins that live here full time around Hilton Head, not every dolphin will learn strand feeding as a hunting technique. While both males and females can strand feed, it’s thought the majority of the strand feeders will be female. Visual observations have shown females strand feeding in small groups while their calves stay near observing the action, learning. Even within the female population, its estimated less than 20% will learn strand feeding as a hunting technique.

female dolphin practicing strand feeding

Where to find the strand feeders?

Those dolphins that do strand feed are quite selective on where to do it. Conditions have to be just right. The tide must be low enough to limit fish from escaping back into deeper water. The mud flats have to be the proper angle; too steep and the fish will be able to roll back into the water. Too flat and the dolphins risk getting themselves stuck on the shoreline. Our private dolphin tours on Hilton Head have had the best luck finding them in the smaller creeks that lead to the Calibogue Sound.

strand feeding dolphins in Hilton Head

Right side only!

Dolphins that strand feed will only do so on the right side of their bodies. This brings up some interesting points and some questions that scientists are still working on. Dolphins don’t have the jaw strength to chew their food, so when they feed, the eat things they can consume whole. They do, however, need their teeth to capture their prey. While strand feeding, dolphins are taking in mud, shells, and bits of cordgrass and detritus. These things can damage their teeth over time and wear down the enamel, rendering them useless to grab things over time. Dolphins appear to be aware of this. By strand feeding strictly on one side, they only risk damage to that side of their mouths, leaving a perfectly intact side of teeth to catch prey in the open water.

Why they choose the right side over left is still a mystery to science. It could be a choice due to physiological makeup of the location to the air passage within the blowhole in relation to the pharyngeal aperture within the pharynx that allows them to swallow, or some other anatomical limitation that makes the right side a more preferable feeding side. There are still many things we don’t know about dolphins.

How can you see dolphins strand feeding?

Here around Hilton Head Island, the best way to see dolphins strand feeding is by boat. While we offer Private Dolphin Tours throughout the day, the best opportunity to find strand feedings are at departure times just before dead low tide. Feel free to call us at 843-247-8117 to coordinate an outing to coincide with the tides.

Strand feeding is truly one of the most remarkable feats in nature to witness. To see the coordinated effort put on by these beautiful creatures is something you must see to believe. If you have an interest in reserving a dolphin tour on Hilton Head Island, or just want to get out on the water and see the amazing wildlife our island has to offer, get in touch with us to reserve your private boat charter today!

Family tour getting a view of a lifetime

Muddy Waters

Healthy waters are a staple of healthy island life. While visiting the Island, a lot of visitors will ask about the quality of our water.  They see its brown or green coloration and think it must not be very clean.  There’s a natural inclination to see something murky as unhealthy.   Not only is our water healthy, but its some of the cleanest sea water you’ll find on a coastline! The murkiness you see comes from two things; how much life is in the water and what attracts that life into the water; our pluff mud.

From dirty pluff mud comes clean water

While not clear, manatees don’t mind the opaqueness of Broad Creek during the summers

Pluff mud is a goopy mixture of soil, dead animal and plant matter. The majority of that dead plant matter is the spartina grass that lines our salt marsh. Pluff mud packs down densely and doesn’t allow oxygen to permeate below a few inches of the surface.  Any type of bacteria that survives in the mud has to create its own oxygen and you can actually smell this chemical reaction at work. As the bacteria create oxygen, they emit a by-product into the air, hydrogen sulfide, giving it a distinct aroma. Many people are convinced its smells like rotten eggs. 

The pluff mud lines the bottom of our tidal creeks and its top layer is constantly moving with the strong currents we have here around the island. This primordial soup of nutrients is continually being kicked up and swirled about, never quite getting a chance to settle. As the current moves at its maximum speed churning up the mud, our waters turn a very ruddy brown coloration. This is the predominate color over winter as cool temperatures control the growth of microorganisms.

The Phytoplankton Cometh

Inside the pluff mud is a large amount of decayed animal and plant matter.  This organic material is called detritus. Detritus breaks down in the salt water and allows microscopic algae known as phytoplankton to feed.  These guys are tiny.  We’re talking a fraction of a millimeter in length.  As the phytoplankton eat the detritus, they release oxygen into the water. Warm temperatures and increased sunlight contribute to their growth. During the hot summer months the amount of phytoplankton increases and, while you can’t see them individually, you can see the effects of the colony. A large phytoplankton bloom will turn the water a greenish color.

Clean Water via the Food Web

plenty of food to go around during the warm summer months

Is all this algae bad?  While some areas of the country face environmental catastrophes due to algae blooms, we don’t have that problem here.  There’s a delicate balance to maintain and the salt marsh does an amazing job of regulating this by creating a food web. The algae that feeds off the detritus in turn becomes food for our oyster beds.  Oysters are constantly filtering the waters here, collecting phytoplankton, other algae and bacteria and pushing out clean sea water.

Other organisms that eat phytoplankton, include zooplankton.  Grass shrimp larva, cannonball jellyfish and sea roaches are common examples. They are voracious eaters, taking in as much phytoplankton as they can. In turn, bait fish, shrimp, crabs, and mobula rays make their way here and feed off zooplankton.  These animals will continue the food web, as larger fish, sharks and dolphins will eat the smaller creatures.  The fecal waste of all the animals go back into the water, becoming detritus, feeds the phytoplankton, and the cycle repeats itself over and over.

Keeping a balance for clean water

It’s important to have a balance within our water column.  Any loss of one organism can have profound and devastating effects on the entire ecology. Loss of oyster habitat, overfishing or taking undersized fish out of the food chain all contribute to the decline to our water quality. Fishing restrictions include time, size and quantity give a species a chance to grow and repopulate without human interference.  On land, building restrictions are in place to limit the amount of harmful pollutants entering our creeks and rivers.  Without these regulations, we run the risk of becoming another environmental catastrophe.

While the waters here may not be crystal clear, you can be assured that they are healthy and clean .  The next time you’re out on a dolphin tour exploring the waterways, you can be thankful that our murky waters bring so much life to our island.

Contact Us

If you have any personal requests or questions about any of our tours, please feel free to reach out by phone, text or email.

(843) 247-8117

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