How Do Whales and Dolphins Sleep?

A question I get asked a lot as a marine biologist is, “How on earth do whales sleep?” And this is, in fact, a very good question. Dolphins and whales belong to a group called ‘cetaceans’ by scientists, and they are, like us, mammals. This means that they breathe air, suckle milk from their mothers and have hair (the ‘hair’ bit has been lost in cetaceans to make them more streamlined). As we all know, most mammal babies sleep a lot of the time – just think of human babies and puppies. In fact, a new born human baby must sleep 17 hours a day. All in all, you will spend about a third of your lifetime asleep! Babies spend so much of their time in “la la land” because sleep is a very important part of development. Sleep is needed for physical growth and for recovery, the immune system, brain development, learning, memory, and information processing as well as many other systems of the brain and the human body.

Sleeping Sperms Whales (image from National Geographic)

It has always been assumed that marine mammals like dolphins and whales babies need as much sleep as infant mammals on land. Therefore, it came as a major surprise when a study by Lyamin and his colleagues (2005) showed that baby killer whales and bottle-nosed dolphins and their mothers hardly sleep after the birth , the days a baby was assumed to be in critical need of sleep. In fact, the babies and their mothers remained mobile and active for 24 hours of the day for the first month, swimming and avoiding obstacles and rising to the surface to breathe.

A Killer Whale mother with her calf (image from hdwallpaperc.blogspot.com)

Cetaceans are different to land mammals in that they need to remember to breath. You and I can simply take a breath of air, and generally not notice that we are in fact breathing – our brains physically regulate our breathing in response to our body’s needs. This is not the case in cetaceans - they have to swim to the surface in order to breath. Just like us, whales and dolphins can drown if they don’t come up for air.  When they do “sleep”, the adults don’t fall asleep completely like we do because they need to be aware of when they need to breathe. Generally, whales and dolphins rest for long periods whilst holding their breath, floating at the surface or resting just as the bottom of the shallow water.

Humpback whales sing and sleep in this strange position! (image from williaminram.com)

The study showed that as the baby got older, both it and its mother gradually increase their time asleep until they reached the sleeping time of normal adults, but never more than that. Cetacean babies simply do not sleep as much as mammals on land. The researchers think that this may be because normal mammal baby sleep behaviour and the importance of this sleep in development and survival simply did not evolve in cetaceans. Whale and dolphin babies may simply not need to sleep for such long periods after birth.

A bottle-nosed dolphin mother and her baby come to the surface to breathe (image from zooborns.com)

 Bottle-nosed dolphin babies need to breathe every 3 to 30 seconds, and when they do the mother keeps swimming which forces the baby to keep swimming. Mom also has to help and support the baby .This doesn’t allow any time for either mom or baby to get much sleep. Previous work has shown that when adult cetaceans sleep, one hemisphere (half) of their brain activity slows and they close either one or both eyes. Mother cetaceans only closed their eyes (either one or both) for less than 1% of their 24 hour day.  Calves less than one month old showed little more eye closure time (1.5% of 24 hours), although these periods were no more than 30 seconds long because the calf needed to breath. This is surprising because such disruptive sleep patterns in other mammals (like humans) is non-restorative, meaning the body gets so little rest you may as well not have slept at all.

A mother and her calf (image from National Geographic)

The study measured the stress hormone cortisol in three killer whale mothers before and after they gave birth. There was no significant increase in the measures after the calf was born, which means that stress did not cause the reduction in sleep behaviour for the mothers - it was their baby's fault!

Four captive bottle-nose dolphins and their calves were observed during their first month after birth. Both showed the same pattern of sleepless behaviour, with neither the mothers nor their caves resting at the surface until they were older than one month of age, after which resting time increased until it was similar to that of normal adults. Injecting cortisol into other male and female dolphins did not change their sleep behaviour. This means that stress was not the cause for the lack of sleep in mothers and their calves – the reason for their lack of sleep is that the calf has to breathe every few seconds and the mother has to help and support it. In the wild, the mother would also have to remain alert to any dangers that may threaten her calf.

Humpack whale mothers and calves stick close together, with the mother helping the calf breathe, stay afloat and safe from predators (image from motelmoka.com)

The ability to remain active and alert helps newborn cetaceans. Constant swimming helps maintain body temperature until they have gained enough weight to develop insulating blubber that will do the job for them in adulthood.

Threats to baby cetaceans include predators like this Great White Shark (image from National Geographic)

This research has changed the way we think about sleep. Other animals, from fruit flies to mammals, suffer severe and sometimes fatal consequences if they do not sleep. Cetacean babies grow and develop just like other mammal babies, despite hardly sleeping. How do they manage? What makes their brains different? The mystery remains to be solved.

The Mystery of the Disappearing Honey Bee

This article is not marine based, but it is a current issue that affects us all and is definitely worth a post. Einstein once said, "If the bee disappears from the surface of the earth, man would have no more than four years to live." The famed physicist never actually said it. But this shouldn’t discourage the fact that bees are a vitally important part of earth’s systems – as pollinators, they are linked to the survival of almost all plant species, but also the crops we depend on as humans. They perform an ecosystem service worth billions of dollars, can you imagine if we had to pollinate millions of acres of crop lands by hand if bees disappeared?

Einstein and his bee (Image from www.insectnewsnetwork.com)

Our indispensible bee heroes are currently however facing a crisis – whole colonies are dying. In 2008 over 11 500 colonies in Bavaria and Germany were affected by a catastrophic die-off. Honey bees were simply not leaving the hives. The investigation revealed that the incorrect application of a pesticide (of the neonicotinoid family) had been spewing toxic chemicals into the air, killing the bees. The European Union wants to ban three of the most common neonicotinoid pesticides that threaten honey bees and other pollinators, and this may happen by the end of 2013. This is all very well and good, but it is also imperative to fully examine the evidence before such a big decision is made. There is as yet no full agreement between scientists as to whether pollinators are exposed to enough pesticides on a under normal conditions to have such a catastrophic effect on their colonies. This is because it is extremely difficult to do rigorous scientifically sound field trials. Pesticide companies obviously say that their product is safe as long as it is used correctly, but the real evidence must come from studies that are not funded by these companies. While we depend on pesticides to produce enough food for our constantly growing population, there is some evidence that the use of neonicotinoid pesticides does not improve crop yield that significantly. So what are we to do?

A honey bee superhero (Image from en.wikipedia.org)

The US based Environmental Protection Agency (EPA) first approved the use of neonicotinoid pesticides in 1994, and they have since become the most widespread insecticide in the world, used in 140 crops and in numerous garden and horticultural products. Most neonicotinoid pesticides work on the more environmentally friendly principle (rather than ‘spraying’ huge areas of crops) of coating the seeds before planting to protect them from soil pests. As the seed grows, it is able to incorporate the insecticide properties from the coating and the young plant is protected as well. This means that a lot less pesticide is used. However, concerns about the affects of these pesticides on other species like birds, earthworms and especially bees are growing – pollinators can be exposed to toxic chemicals through the nectar, pollen or from the seeds themselves. The toxic substances ingested are then invariably fed to the young in the hive, affecting the whole colony.

There is no doubt that high levels of neonicotinoid pesticides do what they are designed to do –they kill insects, even the good, useful ones like bees. However, a multitude of studies in the lab have shown that even low doses can cause damage, influencing the behaviour of the bees. These effects include changes in memory and learning, often leading to bees losing their way or never leaving the hive in the first place. It is difficult however to apply what has been learned about the effects on individual honey bees to the hive as a whole – the colony can carry on even if a lot of bees are lost.

A honey bee fitted with a tiny radio chip to allow researchers to study how movement patterns change after exposure to the pesticides (Image from www.sciencemag.org)

A 2012 study by Goulson and colleagues focused on the effects of neonicotinoid pesticides on bumblebees, because their smaller colony sizes may make them more vulnerable. They found that the colonies exposed to the pesticides had a significantly reduced growth rate, and that fewer new queens were produced (85% fewer in fact) compared to colonies that were not exposed. They concluded that the prolific usage of neonicotinoid pesticides in the developed world may be having a hugely negative impact on wild bumblebee populations, and thus other pollinators.  A number of other studies have been undertaken, some showing negative effects and some showing no effects at all on colonies after  neonicotinoid pesticide exposure. A huge amount of money is going into finding the answer, with one current study funded $950 000 by Bayer CropScience, a manufacturer of pesticides. It seems like the problem is being faced head-on by the companies, they are putting the money out there to find an answer and thus, a solution. Because the survival of bees is everyone’s business.

A bumblebee, as studies by Goulson et al (2012) (Image from www.gizmag.com)

Pollinators are exposed to a cocktail of chemicals, not just neonicotinoid pesticides. For instance, pyrethroids may pose an even greater threat to bees (EPA and USDA, 2013). Commercial hives, used to either produce honey or moved around the country to pollinate various crops can contain as many as 30 chemicals (Frazier etal, 2008). The honey combs themselves accumulate pesticides, making the situation worse over time. The dilemma is that pesticides found in the highest concentrations are used to control a parasitic mite (Varroa destructor) which may be the biggest threat to honey bee colonies (PingChen and Siede, 2007). Without the insecticides, the mites destroy the colony.

A honey bee with a mite (Varroa destructor) visible on the side of its body (Image from www.alexanderwild.com)

Despite the uncertainties, the EU is moving quickly to tighten regulations to protect the honey bee after the European Food Safety Authority (EFSA) released a report clearly stating that neonicotinoid pesticides posed “high acute risks” to pollinators. The European Commission decreed that as of December, farmers won’t be able to plant seeds treated with three neonicotinoid pesticides, nor spray the chemicals on crops preferred by bees. Scientists in industry and the academic world are currently working to make neonicotinoid covered seeds safer by reducing the amount of toxic dust released when the seeds are planted. And breakthroughs are being made. Researchers also continue to investigate how these chemicals affect the wider ecosystem. At least these pesticides are getting the widespread scrutiny they deserve - the world as we know it will cease to exist without bees.