Some populations of beaked whales are considered endangered or threatened. Remember these are rarely encountered whales — if they are so rarely encountered, how do we know how endangered they actually are. This brings up a point I want to cover in the future; we need more naturalist out in the world to keep tabs on the happenings
These whales have some fun features. Several species of beaked whale have a monsterous head (usually referred to as a bulbous melon):
These whales dive deep. Whether any actually dive deeper than Cuvier’s we don’t know, since, again, we known so little about most of these species There are at least 18 other species within this family and we have very little information on most of them.
How do these air-breathing mammals manage to dive so deep? Whales, like us, take a deep breath before they dive. Seals usually exhale and then dive — depleting their lung of air and making diving down easier. This also lowers or stops any continued oxygen exchange with air in the lungs.
A few of the adaptations for deep diving are known and well studied.
- Compared to their body size, whales in general, store a large amount of oxygen - about 5x that of humans. They also store much of their oxygen in muscle - much more, again, than, say, a human: We store about 15% of our oxygen in muscle, while toothed whales, like the beaked whales, store up to 48% of their oxygen in muscle. In addition, the hemoglobin of whales holds more oxygen, so even though the percentage of oxygen in their blood is lower than humans (30 to 57 %) their hemoglobin holds more oxygen at the same partial pressure.(see partial pressure note at end *)
- Lungs collapse. In beaked whales their ribs are collapsable. This causes air to flow out of the lungs and into bronchi, which are more rigid in marine mammals. If the lungs are depleted of air then gas exchange from the lungs stops (or at least slows). A smaller amount of air here, and the subsequently reduced pressure, no doubt protects the thin and delicate alveoli sacs of the lung tissue.
- When whales dive their heart rate drops, called bradycardia. Oxygen is shunted from peripheral organs and tissues — but maintained in the critical areas of the heart and brain.
- Speaking of peripheral organs, beaked whales have large spleens and livers and these might aid there deep diving life style.
Myoglobin is an oxygen binding molecule similar to hemoglobin found in muscle tissue. Whales have higher concentrations of this molecule in their muscles than humans. Myoglobin is smaller - about the size of one of hemoglobins 4 subunits. Myoglobin has a higher affinity for oxygen than hemoglobin (at the same partial pressure — see above — myoglobin will bind more oxygen than hemoglobin). Myoglobin has a single heme group — each hemoglobin has four (one in each subunit). The protein myoglobin helps give the pink color to red meat.
Though impressive even the beaked whales are not perfect divers. A whale doing a deep and long dive still runs out of oxygen and lactate builds up, particularly in the organs that have been shunted and have depended on anaerobic respiration for the dive. The build up of lactate and this adds to muscle fatigue*. Multiple long dives in quick succession are rare.
Besides their deep diving finesse beaked whales have other interesting features. These whales have an unusual feeding motion where they suck in their prey — before presumable grabbing if with their teeth. (They feed on squid and fish). This adaptation appears to be an ancient one, suggested by fossils records of skull shape. They gather is large groups, called pods, at times.
On another not, unfortunately, beaked whales, like several other species, have been involved in mass strandings. In some species most of the information we know about them has been gathered from stranded whales.
*2. Muscle fatigue note: During muscle fatigue much more is happening beside lactate build up.
A few readings
Bianucci, G; I Miján, O Lambert, K Post, O Mateus. 2013. Bizarre fossil beaked whales (Odontoceti, Ziphiidae) fished from the Atlantic Ocean floor off the Iberian Peninsula. Geodiversitas 35: 105–153.
Kooyman, GL., MA Castellini, RW, Davis. 1981. Physiology of diving in marine mammals. Annual Review of Physiology 43: 343 - 356. Quote above is from here.
Moore, JE. and JP Barlow. 2013. Declining Abundance of Beaked Whales (Family Ziphiidae) in the California Current Large Marine Ecosystem. PLoS One 8: e52770.
Snyder GK. 1983. Respiratory adaptations in diving mammals. Respiratory Physiology 54: 269-294.