Blackfish Strandings

Until well into the 19th century, many people living in coastal communities made a living by scavenging shipwrecks. They were called wreckers. Everything that washed up on shore from shipwrecks was profitable, including actual money, raw and manufactured products, and booze. Lawson, author of the first American natural history book, met a Scotsman living off the coast of South Carolina who recovered barrels of oatmeal…ironically a long-term supply of his favorite food. Other wreckers grew vegetable gardens scavenged from shipwrecked seed. They also salvaged wood from wrecked ships that they used for firewood or construction. Another source of income for wreckers were stranded whales. These produced more meat and fuel in the form of blubber than they could use or sell. Following a whale stranding, kids would show up with pieces of bread to eat with fresh blubber. Blackfish often suffer mass strandings. Blackfish are actually whales, not fish, and are today more commonly known as pilot whales. Modern concerned citizens try to rescue pilot whales when they get stranded on shore because the whale’s own weight will suffocate them, if they are out of water for any length of time, but formerly they produced an economic boon for the local populace.

Humans herded blackfish pods to the shore when they were close to stranding. It was a huge economic boon for them. During the Pleistocene blackfish strandings provided a feast for carnivores and scavengers.

The reason pilot whales (Globicephala sp.) strand in large numbers is still a mystery. Pilot whales use electro-magnetic fields to navigate, and some think temporary changes in earth’s electro-magnetic field causes pilot whales to get confused and swim off course. Magnetic rocks on the coast of New England may contribute to pilot whale strandings. Others think noise pollution from ships causes mass strandings, but these strandings occurred long before noise pollution was common. Pilot whales live in pods in the hundreds, and they subsist on a diet of fish and squid. There are 2 species of pilot whales (the long-finned pilot whale G. melas and the short-finned pilot whale G. macrorhynchus). The short-finned pilot whale occurs globally in temperate and tropical waters; the long-finned occurs in the higher latitudes. The long-finned pilot whale lived in the northern Pacific as recently as 2000 years ago but is now extirpated there.

Pilot whale range map. The green represents the long-finned pilot whale range, and the blue represents the short-finned pilot whale range. They overlap in some regions. Long-finned pilot whales occurred near Alaska and the Bering Sea until about 2000 years ago.

Long-finned pilot whales along with at least 3 other pairs of cetacean species have a similar range distribution. One subspecies of long-finned pilot whale lives in the colder waters of the northern hemisphere, and the other subspecies lives in the colder waters of the southern hemisphere. Scientists, using DNA from mass pilot whale strandings over a 30-year period, found low genetic diversity, despite the species being found over such a wide area. A statistical model suggests the northern and southern pilot whale populations became isolated from each other during the Last Glacial Maximum before 12,900 years ago. At least 3 other pairs of cetacean species have the same curious range distribution. These include right whales (Eubaleana japonica and E. australis), right whale dolphins (Lissodelphus peronii and L. borealis), and harbor porpoises (Phocoena phocoena and P. spinnipinnis). The speciation between these species must be related to changes in ocean currents that altered water temperatures and led to isolation of populations and divergence.

I was unaware of this cetacean species until I was researching this article. The right whale dolphin is the only species of dolphin without a dorsal fin.

Reference:

Kraft, S; M. Perez-Alvern, C. Olavarria, and E. Paulis

“Global Phylogeography and Genetic Diversity of the Long-finned Pilot Whale Globicephala melas, with New Data from the South Pacific”

Scientific Reports 10 (1769) 2020

Flawed Study Suggests Anthropogenic Fires Caused the Extirpations of Megafauna Near the La Brea Tar Pits

A group of scientists think they’ve found the answer to what caused the disappearance of most of the megafauna species that lived near the La Brea Tar Pits. They took sediment cores from several sites near the tar pits and measured the quantities and composition of pollen and the amount of charcoal present–an indicator of fire frequency. They radio-carbon dated the layers of the core. They also used radio-carbon dates from 172 specimens of megafauna species in the region including saber-tooth, giant lion, dire wolf, coyote, bison, camel, horse, and ground sloth. They fed this data into a statistical model and concluded as the climate became warmer and drier, the environment became more susceptible to fires set by increasing populations of humans. The anthropogenic fires transformed the landscape from juniper-oak woodlands into a semi-arid chapparal, and the only surviving megafauna species (that they studied) was coyote. (A chapparal is a dry landscape covered in pine, shrub, flowering herbs, grass, and cactus, and the climate consists of mild winters and hot summers.) These extirpations in Southern California occurred about 1,000 years before the extinctions in the rest of the North American continent, but they occurred at the same time these species were in decline elsewhere. Camels and ground sloths disappeared a few hundred years before the other species in this study, but I should note (which this study does not) that the most recently dated specimen was likely not the last surviving member of the species–there still could have been a considerable population that perchance left no fossil evidence. A serious flaw in the conclusion reached by this study occurred to me.

This illustration is a ridiculous exaggeration, and I think it is based on a seriously flawed assumption. From the below referenced study.

List of species used in the below referenced study and their final extirpation date estimates.

The authors of this study assume the transformation of juniper/oak woodlands to a dry chapparal environment resulted in the local extirpations of megafauna here. The problem with this hypothesis is that at least 3 of the species used in this study thrive in semi-arid chapparal like environments. Lions live in semi-arid environments all across Africa. Wild horses are most common in the American southwest where they roam deserts. And camels, of course, are known to live in arid environments, and today introduced wild camels survive in Australian deserts. I realize the North America Pleistocene versions of these species are not exactly the same as modern species, but they were highly adaptable and lived all across North America, and they endured all kinds of sudden dramatic shifts in climate, including peak Ice Ages which caused widespread arid conditions. I seriously doubt a shift to more open drier conditions negatively affected horses, camels, and lions. I think populations of these species would increase in this type of environment.

Horses thrive in the semi-arid type of environment that the below referenced study erroneously assumed caused their extirpation in southern California.

Camels also can endure semi-arid conditions. I think the authors of this study blundered in their conclusion.

19 scientists put their name on this paper. I find it hard to believe this obvious flaw in their conclusion occurred to none of them. It occurred to me before I finished reading the paper. I contacted the lead author of the paper and pointed out this flaw, but so far, he has not responded. It seems as if scientists want to bridge the gap between climate models of extinction with those who hold humans are solely responsible. Put me in the latter camp. The increase in fire frequency is proxy evidence for the presence of humans. Direct hunting by humans increased megafauna mortality above the ability of these large slow-reproducing animals to maintain their populations. It was overhunting by humans, not a change in fire regime that caused the extinction of these species. It is the simplest explanation, and the only one that makes sense to me.

Reference:

O’Keefe, R. et. al.

“Pre-Younger Dryas Megafaunal Extirpations at Rancho La Brea Linked to Fire-Driven Shift”

Science August 17, 2023