Bahamas 2000
Dolphins sometimes carry weapons
25 Nov 2015

Dolphins sometimes carry weapons

*The following blog post is an excerpt from the book Twenty-Two Fantastical Facts about Dolphins*

Psychologists have learned that holding an otherwise innocent object in your hand – like an umbrella – makes onlookers perceive you as more dangerous than if you were empty-handed. This same, subconscious fear of weapon-like objects is lodged in the minds of many of our primate cousins. Our closest relatives – chimpanzees – appeal to this weapon-fear bias by waving tree branches and logs in the air when trying to make themselves look larger and more intimidating. And by golly it works. As anyone who has spent time in the African jungles can attest to, a giant male chimpanzee screaming and running at you with a tree-branch in his hands is full-on terrifying. This is one of the reasons I prefer to study dolphins. They don’t have hands, so the chances they will club me or my fellow researchers to death in the open ocean are small.

Or so I thought.

It now appears that dolphins are known to wield weapons too. The Amazon river dolphin – also called the boto – has been observed carrying tree branches in its mouth. Since these river-bound dolphins live quite close to vegetation, it’s easy enough for them to get their hands mouths on weapon-like objects. They have been observed jutting their heads out of the water and waving sticks or branches around – a lot like chimpanzees.

Why do botos do this? Nobody has witnessed them actually assaulting other botos with their makeshift weapons, so it’s probably not meant as a tool to punish rivals. Then again, chimpanzees usually don’t hit each other with sticks – they just brandish them as a means of looking tougher. This is probably what is happening with the botos as well. It’s almost always the males who engage in this stick-thrashing behavior, and almost always when they’re around other males. Most of the time, these stick-carrying bouts end in some sort of aggressive encounter between the males. Tail slaps, biting, ramming – all kinds of unfriendly dolphin stuff.

Unsurprisingly, stick-wielding is often witnessed at times of the year when the females are most fertile. So it seems likely that males are trying to impress the ladies or otherwise scare their rivals by carrying weapon-like objects in their mouths. It might well be that the male dolphin who carries the biggest stick also has the best luck when it comes to mating.

Carrying sticks or other objects is an awkward thing for a dolphin to be doing. It will slow them down as they swim, and make it impossible to eat. Like much of dolphin behavior, it’s still a mystery as to why they do this. But I can guarantee you that a giant male Amazon river dolphin charging at me with a stick in its mouth is enough to keep me from wanting to swim in the Amazon. Well, that and the piranha.

 Want to read more zany dolphin science trivia?  Order a copy of the book Twenty-Two Fantastical Facts about Dolphins

 

 

 
Dolphins don't sleep
23 Nov 2015

Dolphins don't sleep

*The following blog post is an excerpt from the book Twenty-Two Fantastical Facts about Dolphins*

Almost all animals that live in the ocean are able to breathe water – extracting the life-giving oxygen that’s swishing around in seawater with their gills. Crustaceans, fish, clams, amphibians – they all have gills, and don’t need (and generally prefer to avoid) air. But marine mammals – which include dolphins, whales, seals, manatees, sea lions, otters and a handful of others – still need access to air in order to get their oxygen. The ancestors of all marine mammals were air-breathing land-animals, and during their millions-of-years-long return to the ocean, none of them bothered to evolve gills or other anatomical features that would allow them to stay submerged in water 100% of the time.

Thanks to the “whatever, that’s good enough” attitude of evolution, dolphins are forced to stick their blowholes out of the water every few minutes in order to fill their lungs with oxygen-rich air. Some species can hold their breath longer than others, but most need to be at the surface a few dozen times every hour to breathe.

But if dolphins need to swim to the surface to breathe at regular intervals, how then do they ever get any sleep? Some species – like pilot whales – engage in behavior called logging where they float on the surface of the ocean with their blowholes above the waves. This seems a pretty logical way for a dolphin to sleep since it’s able to keep its airway exposed at all times. But the thing is, most species of dolphin don’t sleep at the surface like this.

In fact, dolphins don’t really sleep at all.

When humans fall asleep, our conscious minds shut down, leaving the more primitive parts of the brain found in our brainstem – like the medulla oblongata – to take care of unconscious processes like breathing or making the heart beat. But the medulla oblongata in dolphins does not control their breathing. Dolphins must think about every breath they take using the parts of the brain that – in humans – is mostly shut off when we sleep. This means that dolphins need to remain conscious at all times or they simply stop breathing. In fact, if a dolphin ever does lose consciousness – like if you give it a general anesthetic – it will suffocate pretty quickly.

Luckily, dolphins have evolved a workaround. All animal brains must enter periods of sleep or restfulness in order to survive. Nobody is really sure why, but if an animal is denied sleep for long enough, it will die. Dolphins have found a way to get the rest they need by sleeping one half of their brain at a time. Dolphin brains, like all mammal brains, are divided into two hemispheres. Dolphins are able to shut down just one hemisphere at a time and enter into something called unihemispheric slow-wave sleep. This allows for one half of their brain to go offline while the other stays awake, so dolphins can continue swimming, watch for predators, and return to the surface to breathe with the awake part of their brain.

Dolphins in this half-asleep mode usually swim lazily near the surface. Each half of the brain will sleep for a couple of hours before waking up and letting the other half get some shut-eye. And it really is shut-eye in most cases – you can usually tell which half of a dolphin’s brain is asleep by looking at their eyes: the one connected to the sleeping half is shut while the other one is open. Dolphins often sleep like this at night time, and typically for about 8 hours per day – not unlike most humans. Well, except for the half-closed-eye thing.

Scientists have tested dolphins to see just how awake they really are when sleeping one half of their brain. In one experiment, dolphins were asked to touch a paddle every time they heard a tone. The tone was played at random every few minutes. Researchers kept producing the tones all day and all night for days at a time without the dolphins messing up, or even displaying signs of being tired. The experiment ended after 5 days, but probably could have been kept up forever. The dolphins, you see, weren’t tired because they were able to sleep one half of their brain as needed, with the other half wide-awake and able to concentrate on the (really boring sounding) paddle task.

When it comes to staying awake and maintaining constant vigilance, it’s dolphin mothers that are the true insomniacs. Newborn dolphins hitch a ride with mom by swimming right next to them, getting sucked into the wake that their mother’s body creates while she swims through the water. If a dolphin calf positions itself in just the right spot next to mom, it will be propelled through the water without having to swim very hard, which helps it conserve energy. In order to make sure their newborns stay afloat and don’t get too tuckered out, dolphin mothers need to keep swimming at all times in order to create this protective swim-bubble for their calves. Spend too much time logging near the surface, and their little ones might sink. So dolphin moms just keep swimming without a break for days/weeks/months until their calf is strong enough to handle the world on its own. They likely engage in unihemispheric slow-wave sleep at some point, but to the casual observer it looks like they don’t sleep at all.

Based on my own experiences raising a human infant, this “total lack of sleep for months at a time” thing sounds pretty familiar…

Want to read more zany dolphin science trivia?  Order a copy of the book Twenty-Two Fantastical Facts about Dolphins

 

 

 
Dolphins almost never drown
18 Nov 2015

Dolphins almost never drown

*The following blog post is an excerpt from the book Twenty-Two Fantastical Facts about Dolphins*

Being an air-breathing animal living in the ocean brings with it a number of challenges. Chief among them is trying not to drown. The paradox/problem of living in an aquatic environment but needing to be at the surface to breathe is something that manatees, sea turtles, whales, and dolphins have to cope with on a daily basis. But for dolphins, drowning in the traditional sense (which involves inhaling water into your lungs) is not really the problem.

Dolphins, you see, are sort of immune to drowning.

I know what you’re thinking. This sounds like crazy nonsense. Don’t hundreds of thousands of dolphins drown in fishing nets each year? Well yes, a huge number of dolphins are killed by fishing nets each year. But no, most dolphins trapped in nets don’t drown.

They suffocate.

What’s the difference? It all has to do with what’s happening with a dolphin’s blowhole when they are trapped under water. Dolphins are conscious breathers. This means that a dolphin must think about and decide on every breath it takes. Humans, in contrast, have the ability to let our brainstem take over the breathing duties, allowing us to continue to take breaths even when unconscious or asleep. Dolphins do not have this luxury.

This conscious-breathing setup means dolphins have evolved a strange relationship with their blowholes. A dolphin’s blowhole – which is the only pathway to a dolphin’s lungs – is closed by a sort of flap, which is attached to a very strong set of muscles. When closed, this flap creates a water-tight seal. The blowhole flap remains – by default – in the closed position. Below the blowhole are a series of internal flaps, valves, and other fleshy portals all of which create their own airtight seals – essentially creating four separate barriers between the outside air and a dolphin’s lungs. So if a dolphin is just hanging about in the ocean not thinking about taking a breath, it doesn’t have to worry about letting water into its lungs – the blowhole and other muscle-seals are tightly shut, and waiting on orders from the dolphin’s conscious mind to open up and let in air.

This means that if a dolphin were to ever be knocked unconscious, he/she would sink to the seafloor, and come to rest at the bottom with their blowhole firmly shut. Should the dolphin fail to awaken before they run out of oxygen, they will die – not from drowning (that is, inhaling water), but from suffocation.
Something similar happens if a dolphin were to be trapped in a fishing net. Humans, when trapped under water and in desperate need of air, will almost always open their mouths and make one final, desperate attempt to breathe, sucking water into their lungs. It is rare for a human to suffocate under water without taking a final breath that fills their lungs with water.

A dolphin, on the other hand, is far less likely to inhale water this way. Although they might crave air just as desperately as a human, the blowhole and sphincter-seal system in their nasal cavity typically remains in the default, shut position.

Occasionally, dolphins that are sick might accidentally inhale water and drown if they are too weak to keep their heads above water. And some dolphins trapped in nets are so overcome by panic that they are able to override the seal-system and open their blowholes, allowing water into their lungs.

But it is likely that most dolphins trapped in a net will ultimately succumb to suffocation as they run out of oxygen, and die with their blowhole closed. This is a terrible, if all too common fate for a dolphin, or any other air-breathing sea creature.

Want to read more zany dolphin science trivia?  Order a copy of the book Twenty-Two Fantastical Facts about Dolphins

 

 

 
Dolphins sometimes have backward dorsal fins
16 Nov 2015

Dolphins sometimes have backward dorsal fins

*The following blog post is an excerpt from the book Twenty-Two Fantastical Facts about Dolphins*

Spinner dolphins are pretty bizarre as far as dolphins go. Their habit of leaping out of the water and spinning around at high velocity is just odd – not something other species of dolphins usually do. It’s made even more bizarre by the fact that nobody knows why they do it. It might be to shake off pesky suckerfish that are latched onto their sensitive skin. Or maybe it’s a form of communication, or a mating display. Or, as is likely the case for lots of dolphin behavior, it’s just something fun to do.

It’s not just that spinner dolphins act strange. They also look strange. An adult male spinner dolphin typically has a huge bump just behind its genital area called a ventral hump. The older a male dolphin is, the bigger its hump. So what’s in the hump? Nothing important really – mostly connective tissue. And what’s the point of a hump? Like many weird anatomical structures seen only on males of a species (like moose antlers or peacock tails), its sole purpose is to advertise how strong/awesome the male is, which both intimidates rivals and attracts the lady dolphins. Some other species of dolphins, like common dolphins, also grow a little hump for similar purposes. But nothing rivals the size and prominence of an adult male spinner dolphin’s crazy-looking hump.

Adult male spinner dolphins also have an impossibly strange-looking dorsal fin. It looks exactly like it’s been stuck on backwards. Instead of the fin curving from front to back – like you see in almost all other dolphin, shark, and fish species – it curves towards the front. As the males age, their dorsal fins change shape. When they are young calves, their fins are the normal size and shape. But once they reach full maturity, the fin loses its backwards curve and looks more like a triangle. As they continue to age, it starts pitching forward.

So what’s going on here? Probably more of the same “check me out ladies” kind of shenanigans that you find with their ventral humps. It might be the case that a backwards fin makes it harder to swim, so if an adult male can still manage to be at the top of his game with this kind of physical “handicap,” then other males know to leave this tough-guy alone. And the ladies will know that he’s probably good dad-material. Female spinner dolphins also have a reverse-fin sometimes, so it’s not just a male thing.

Male spinner dolphins also have odd-looking upturned or curled tail flukes. This might be yet another anatomical oddity that is meant to attract the ladies. Or it might help them swim faster. Nobody knows. Bottom line: adult male spinner dolphins look like they’ve been crafted out of playdough by a toddler who has no idea what a dolphin should look like.

Want to read more zany dolphin science trivia?  Order a copy of the book Twenty-Two Fantastical Facts about Dolphins

 

 

 
Dolphins have ears in their jaws
13 Nov 2015

Dolphins have ears in their jaws

*The following blog post is an excerpt from the book Twenty-Two Fantastical Facts about Dolphins*

Whales and dolphins evolved from furry mammals with hoof-like feet that roamed the Earth 50 million years ago. Called Pakicetus, these animals looked like a cross between a dog, a cat, and a tiny, angry hippopotamus. They walked on four legs, had a snout with eyes on the front of their heads, and sported cute little gerbil-like ears.

As natural selection began the process of transforming Pakicetus into the modern-day dolphin, the ancestors of dolphins lost many anatomical features that weren’t helpful to them in their new aquatic environment. They traded in their body hair for a thick layer of blubber to help keep them warm. Their gangly limbs were transformed into sleek flippers and flukes – far more useful for propelling them through the water. And those cute little gerbil-ears – which would have slowed them down in the water – disappeared altogether.

The visible part of Pakicetus’ external ear – that floppy little pancake that most extinct and living mammal species have on the sides or tops of their heads (including humans) – is called an auricle or pinna. It acts almost like a satellite dish that amplifies sound and directs it toward the ear hole. If you look closely at the side of a dolphin’s head, you can still see a tiny pin-prick where their ear hole is, but the pinna itself is completely gone.

 But it wasn’t just the pinna that underwent a radical change as Pakicetus evolved. The strangest transformation took place under the hood. The tiny ear hole seen in modern dolphins, which originally transported sound waves to the middle or inner ear, no longer serves any purpose at all. Dolphins’ ear canals are completely blocked up with fibrous tissue, ear wax, and other fleshy debris. Sound is no longer able to make its way from a dolphin’s ear hole to its inner ear.

How then do dolphins hear at all? This was a question that stumped scientists back in the 1940s when they first began examining dolphins’ hearing anatomy. Dolphins clearly have very sensitive hearing, and are able to detect sounds at extremely high frequencies, well beyond what a human or even a dog could hear. But how were dolphins transporting sounds from the outside world into their inner ears if they had blocked-up ear canals?

It turns out that all the work that used to be done by the pinna – amplifying sound and directing it to a dolphin’s inner ears – is now done by a dolphin’s lower jaw. A dolphin’s jaw is filled with a kind of fatty substance that leads directly up into their middle ear. As sound waves travel through the water, they are absorbed by the dolphin’s jaw and are directed up along this fatty canal. With a jaw bone on each side of its head, a dolphin is able to use its jaws much like we would use pinna on the sides of our head – allowing them to pinpoint where a sound is coming from. And since the fat in their jaws is similar in density to water, this allows sound waves to travel easily to their inner ears.

This fancy new lower-jaw hearing system is made extra effective with the help of dolphins’ teeth. The more-or-less evenly spaced rows of 22 teeth that dolphins have in each jaw actually help them to amplify sound. Their teeth act a bit like an antenna, with the teeth resonating at frequencies that dolphins use for their echolocation. This hearing system likely evolved in tandem with dolphins’ echolocation ability.

Although dolphins might have lost their cute gerbil-ears, they appear to have traded them in for some rather sophisticated auditory technology. It’s yet another bizarre feature of an animal that has taken a rather unorthodox evolutionary path.

Want to read more zany dolphin science trivia?  Order a copy of the book Twenty-Two Fantastical Facts about Dolphins

 

 

 

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DCP 2015 RIMS Reseach Video

Curious about our recent research trip to the Roatan Institute for Marine Sciences (RIMS)? Check out our latest research video!

https://vimeo.com/144932875?utm_source=email&utm_medium=vimeo-cliptranscode-201504&utm_campaign=28749

A big thank you to John Anderson of Terramar Productions!

DCP's RIMS 2015 Data Summary
02 Nov 2015

DCP's RIMS 2015 Data Summary

Our 2015 field session at Anthony's Key Resort's Roatan Institute for Marine Science (RIMS) was a success! We were able to collect six hours of video with the MVA2 camera as well as another ~9 hours of video with 1-2 GoPro cameras. That is, for all sessions, one GoPro was mounted above the MVA 2 facing forward to provide a wider view and greater area for confirming dolphin IDs from body parts that might be slightly out of view on the MVA camera but in range on the GoPro. And, for about 1/3 to 1/2 of the sessions, we also borrowed Bill's GoPro and placed it atop the MVA2 but pointing at me/behind me. This allowed us to see who might be behind me!

Yes, it is true, there are times the dolphins are more playful than I want them to me ... with me! They pull at my fins and circle swim around me and the MVA2. With the added view behind me, I can tell when a dolphin is there, while doing analysis!

We began confirming IDs from the video tapes on Roatan, but the video logging will begin in earnest later this week. I'll also go through the tapes, and still images, to draft sketches of all 20 dolphins we observed last week. Though the analyses takes much longer than data collection, I really enjoy this part of the process. It's where patterns become evident in the data!

We'll provide an update on data processing in the next two issues of the Dolphin Gazette! And, I'll continue to swim laps and practice my yoga (thanks Joy - www.prananda.com) to keep myself in shape for following dolphins in the spring (returning to RIMS in March 2016 with a student group!).

Thank you for your support!

Cheers

Kathleen & the DCP RIMS 2015 team!

Our Last Day - data and a swim!
31 Oct 2015

Our Last Day - data and a swim!

Today, Friday, dawned bright after an evening of thunderstorms that affected the early AM underwater visibility. Still, I was able to collect data during an early morning session and a second morning session on our last day at RIMS/AKR for 2015. Champ and Calli were as attentive as ever to me in the early morning as were French, Ronnie and Ritchie. Even Bailey spent a bit of time investigating the hydrophones.

The second morning session brought better underwater visibility (up to ~3.5 meters but still silty). And, I was able to observe Paya and Maury swimming together in a group that also included Beasley, Alita, Gracie and Tilly. Tilly is growing by leaps and bounds but still hangs more with her mom, Gracie, than any one else. At least while I am observing!

Our DCP RIMS 2015 team spent some time in the water with the dolphins today also! They had an encounter Maury on the beach, as you can see in this photo, and then swam for about a half hour with the group. Several games of seaweed toss and tag were enjoyed by all! Members of our team also enjoyed the dolphins' vocalizations - many whistles and echolocation click trains were audible.

Tomorrow is our travel day home - and Halloween! Bill regaled us with his pirate costume this evening ... He got his trick-or-treating in a day early since I doubt they will allow it on the plane!

I'll upload a summary of our data collection details once I've returned home and caught up a bit.

Thanks for reading and sharing our field season from afar!

Cheers

Kathleen & the DCP RIMS 2015 team!

Our Mornings Start Early!
30 Oct 2015

Our Mornings Start Early!

Even as our week begins to wind down, our mornings start early. This DCP team is a group of early risers! Perfect for catching the morning sun, best underwater visibility and social dolphins! You can see everyone preparing to take their positions around the enclosure for the best observer positions ... and maybe also for the occasional game of seaweed toss with the younger dolphins!

This morning presented the best underwater clarity of the week, so far. Very little silt or precipitate in the water, clear for at least 6 m ... and also social dolphins. Of course, Polly, Calli and Champ were my buddies for much of the session. They are enamored of my fins! (and sometimes of my legs, knees or shoulders!).

It was neat to watch the social interaction and the pairs in their swims. Maury was hanging with Paya (as seems to be typical). Beasley and Bailey were swimming together a few times, and also Bailey was with Alita for a few minutes. The 3 and 4 year old dolphins were all rolling all over each other and whistling with bubble streams from their blowholes! The late morning session had many of the dolphins more subdued. They were less social and more resting, except for the youngsters! They hardly ever seem to tire!

Tomorrow is our last morning of data collection ... and our team will have their encounter/swim program. It should be fun and I will enjoy watching them get time in the water with the dolphins!

Until tomorrow

Cheers

Kathleen & the DCP RIMS 2015 team!

Contact Us

Write to us via snail-mail at:

Dolphin Communication Project
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