I was just reading over another recent paper that may also prove relevant to this post as well as the previous one, so I thought I would post an update.
Site fidelity in cetaceans is not new, but a recent paper by Valenzuela et al (2009) does an excellent job showing that for at least some large mysticetes, site fidelity is a matter of cultural inheritance, and can cause a lack of flexibility (at least in the geologically speaking 'short term') of feeding grounds for some taxa even in bad years.
Obviously, this report does not bode well for balaenids in the oncoming global warming situation, though it may be another facet worth exploring when considering prehistoric cetacean distributions. It may ultimately be outside the realm of possibility to answer such questions, particularly when we still don't have good estimates of simple things like body size of fossil groups (though I know one person is working on that) or how far different taxa may have regularly migrated (which may or may not be consistently related to body size).
Tuesday, June 9, 2009
Monday, June 8, 2009
Cetacean response to climate change
A very recent review paper by Colin McLeod (see here for Univ Aberdeen press release) in Endangered Species Research, titled, "Global climate change, range changes and potential implications for the conservation of marine cetaceans: a review and synthesis", raises some critically important points about the distribution of whales and how that is likely to be affected by expected changes in global climate. Obviously, this is very, very important for all of us that care about modern Cetacea as well as the health of the world's oceans in general.
But I would also urge marine mammal paleontologists to consider something else about this paper. Note that McLeod goes through and meticulously reviews the preferred habitats of most modern cetaceans. One should not be surprised to find that very few of these have a fossil record that goes back to the middle Miocene, when the world was much warmer, and the typical polarized distribution of modern cetaceans is, in reality, an effect of the repeated expansions and contractions of many cetaceans that have evolved in favor of colder waters (and its associated productivity) several times within the last 2-3 million years. This antitropical distribution splits sister species from each other by a warm patch of water in tropcical (and sometimes even subtropical) zones.
The conundrum in making the fossil record of whales informative of the problems we are facing today is that the fossil record of cetaceans is best for the Miocene, from a time when they were experiencing a cooling trend, not a warming. The fossil record of cetaceans during the Pliocene and Pleistocene may be better suited for such a comparison to the modern situation, but it is simply not as well studied (or perhaps as abundant) as the Miocene fossil record is. In that way, if one were to try to predict how marine mammals would respond to a warming trend, it would probably be ideal to very carefully explore how they handled this during glacial-interglacial cycles.
BUT, one edge that the Miocene (and likewise late Eocene) has over these glacial times is some insight in the way that cetaceans interact in marine ecosystems that are warm, like those that will eventually come with the changes being wrought on our world. If one wants to best understand how cetaceans may interact when warmer waters dominate the ocean landscape, the Miocene is perhaps a better model system than even the present day. Granted, modern animals are still FAR more important to understanding their future than any fossil taxon (with its own phylogenetic baggage to deal with that could influence the data), the total community structure, distribution patters, and even physical interactions may be in part better understood when looking at an almost worldwide warm world full of cetaceans in the Miocene. For instance, there are clear differences in the distributions of platanistids and eurhinodelphids in the West Atlantic during the Miocene, and better understanding why such similar animals would have latitudinally partitioned a very warm coast is almost impossible to understand from today's taxa, even though it may happen to many of today's species in the not too distant future.
If there are any graduate students looking for projects out there, one I can easily see would be ones utilizing some of Colin McLeod's other work on correlations of prey size and osteological correlates to answering these sorts of questions. Likewise, other groups that have a different response to climate change, seacows, may be a worthwhile avenue to explore some of these questions as well. I wish I could do it all, and though I am trying to get a start with the Sirenia part of the equation, in the end there are too many questions for one person to ask in a lifetime, and I hope someone out there will give some of these studies with cetaceans a try.
But I would also urge marine mammal paleontologists to consider something else about this paper. Note that McLeod goes through and meticulously reviews the preferred habitats of most modern cetaceans. One should not be surprised to find that very few of these have a fossil record that goes back to the middle Miocene, when the world was much warmer, and the typical polarized distribution of modern cetaceans is, in reality, an effect of the repeated expansions and contractions of many cetaceans that have evolved in favor of colder waters (and its associated productivity) several times within the last 2-3 million years. This antitropical distribution splits sister species from each other by a warm patch of water in tropcical (and sometimes even subtropical) zones.
The conundrum in making the fossil record of whales informative of the problems we are facing today is that the fossil record of cetaceans is best for the Miocene, from a time when they were experiencing a cooling trend, not a warming. The fossil record of cetaceans during the Pliocene and Pleistocene may be better suited for such a comparison to the modern situation, but it is simply not as well studied (or perhaps as abundant) as the Miocene fossil record is. In that way, if one were to try to predict how marine mammals would respond to a warming trend, it would probably be ideal to very carefully explore how they handled this during glacial-interglacial cycles.
BUT, one edge that the Miocene (and likewise late Eocene) has over these glacial times is some insight in the way that cetaceans interact in marine ecosystems that are warm, like those that will eventually come with the changes being wrought on our world. If one wants to best understand how cetaceans may interact when warmer waters dominate the ocean landscape, the Miocene is perhaps a better model system than even the present day. Granted, modern animals are still FAR more important to understanding their future than any fossil taxon (with its own phylogenetic baggage to deal with that could influence the data), the total community structure, distribution patters, and even physical interactions may be in part better understood when looking at an almost worldwide warm world full of cetaceans in the Miocene. For instance, there are clear differences in the distributions of platanistids and eurhinodelphids in the West Atlantic during the Miocene, and better understanding why such similar animals would have latitudinally partitioned a very warm coast is almost impossible to understand from today's taxa, even though it may happen to many of today's species in the not too distant future.
If there are any graduate students looking for projects out there, one I can easily see would be ones utilizing some of Colin McLeod's other work on correlations of prey size and osteological correlates to answering these sorts of questions. Likewise, other groups that have a different response to climate change, seacows, may be a worthwhile avenue to explore some of these questions as well. I wish I could do it all, and though I am trying to get a start with the Sirenia part of the equation, in the end there are too many questions for one person to ask in a lifetime, and I hope someone out there will give some of these studies with cetaceans a try.
Thursday, June 4, 2009
Preservation biases of fossil cetaceans
I have been quietly writing a series of posts for this blog, lengthy and full of figures, and now that I am close to posting some of them, I came across something short and sweet that I cannot resist posting about. So, I guess the longer posts will have to wait.
This morning, when I read the newest MarMamm listserv posts, I came across a new paper on minke whale habitat preferences off the coast of Scotland. Several years ago I would never have read that paper, mainly out of a lack of interest in focusing on baleen whales. Since then I have had the pleasure of working more closely with Alton "Butch" Dooley of the VMNH (see his blog). Butch has been finding numerous, well-preserved, mysticete skulls and skeletons in the Miocene age rocks of Carmel Church Quarry in Virginia. These animals are quite a puzzle at times, mainly because of their size they are rarely so well preserved, and the logistics of collecting them has deterred many in the past and resulted in specimens that a few and far between. Anyone working on dinosaurs may know how it feels, but suffice it to say that if you are interested in really understanding fossil species, preservation and sample sizes matter. As a paleobiologist, what Butch is collecting in VA is an ideal and rare opportunity.
Ok, back to the paper of the morning. Kevin Robinson and colleagues in Scotland and Wales very recently published a paper on the habitat preferences of modern minke whales in the journal, Journal of Coastal Conservation. In it, they present a consistent link between the distribution of minke whales (Balaenoptera acutorostrata) and habitat details, such as seafloor physiography and sediment type.
I know this is a stretch, but I cannot help but think that this close connection of some, but perhaps not all, mysticetes to a habitat type might be useful in explaining the distribution and preservation of large fossil cetaceans. I don't mean to push it too far, but this could serve a role similar to the way terrestrial paleo folks regard the lack of montane taxa preserved (or at least, they all should). I know it is logical, but it is nice to find modern support for the idea that the record of fossil mysticetes may be biased to those that prefer habitats that preserve well.
This may also be a point of curiosity regarding how/why we get physeterid fossils, even though physeterids are supposedly more pelagic. I don't mean that fossil physeterids were not pelagic, but it is worth considering all the possible influences on distribution of fossil cetaceans, and maybe use taphonomy to better understand what animals are part of a local fauna, and which are bodies washing into it from afar.
These are all things to think about, although perhaps nearly impossible to approach as a study due to the complications involved in confirming this sort of data widely for modern mysticetes, and even more difficult for attempting to link studies of physiography and sediment types with meticulously collected fossil mysticetes. But, I hope it is an entertaining thought for the day and look forward to any comments you all might have.
Cheers,
Brian
This morning, when I read the newest MarMamm listserv posts, I came across a new paper on minke whale habitat preferences off the coast of Scotland. Several years ago I would never have read that paper, mainly out of a lack of interest in focusing on baleen whales. Since then I have had the pleasure of working more closely with Alton "Butch" Dooley of the VMNH (see his blog). Butch has been finding numerous, well-preserved, mysticete skulls and skeletons in the Miocene age rocks of Carmel Church Quarry in Virginia. These animals are quite a puzzle at times, mainly because of their size they are rarely so well preserved, and the logistics of collecting them has deterred many in the past and resulted in specimens that a few and far between. Anyone working on dinosaurs may know how it feels, but suffice it to say that if you are interested in really understanding fossil species, preservation and sample sizes matter. As a paleobiologist, what Butch is collecting in VA is an ideal and rare opportunity.
Ok, back to the paper of the morning. Kevin Robinson and colleagues in Scotland and Wales very recently published a paper on the habitat preferences of modern minke whales in the journal, Journal of Coastal Conservation. In it, they present a consistent link between the distribution of minke whales (Balaenoptera acutorostrata) and habitat details, such as seafloor physiography and sediment type.
I know this is a stretch, but I cannot help but think that this close connection of some, but perhaps not all, mysticetes to a habitat type might be useful in explaining the distribution and preservation of large fossil cetaceans. I don't mean to push it too far, but this could serve a role similar to the way terrestrial paleo folks regard the lack of montane taxa preserved (or at least, they all should). I know it is logical, but it is nice to find modern support for the idea that the record of fossil mysticetes may be biased to those that prefer habitats that preserve well.
This may also be a point of curiosity regarding how/why we get physeterid fossils, even though physeterids are supposedly more pelagic. I don't mean that fossil physeterids were not pelagic, but it is worth considering all the possible influences on distribution of fossil cetaceans, and maybe use taphonomy to better understand what animals are part of a local fauna, and which are bodies washing into it from afar.
These are all things to think about, although perhaps nearly impossible to approach as a study due to the complications involved in confirming this sort of data widely for modern mysticetes, and even more difficult for attempting to link studies of physiography and sediment types with meticulously collected fossil mysticetes. But, I hope it is an entertaining thought for the day and look forward to any comments you all might have.
Cheers,
Brian
Saturday, March 7, 2009
Yes, another blog....
Ok, I know the world does not need another blog, but I find myself interested in keeping one so that I can share news and ideas more broadly than just with the Aquatic Amniote Paleobiology group I created on facebook.
You are welcome to join that if you wish, but not everyone wants to join facebook, and this way I hope to reach a broader audience. If would really like this to become a place to exchange ideas and discuss matters of aquatic amniote evolution, and evolutionary biology and paleobiology, especially methods and philosophy, openly.
The first real post will be up soon.
Thanks!
Brian
You are welcome to join that if you wish, but not everyone wants to join facebook, and this way I hope to reach a broader audience. If would really like this to become a place to exchange ideas and discuss matters of aquatic amniote evolution, and evolutionary biology and paleobiology, especially methods and philosophy, openly.
The first real post will be up soon.
Thanks!
Brian
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