Why are Blue Whales singing deeper every year?

[Ignis]

All around the world, blue whales aren’t singing like they used to, and scientists have no idea why.

The largest animals on Earth are singing in ever-deeper voices every year. Among the suggested explanations are ocean noise pollution, changing population dynamics and new mating strategies. But none of them is entirely convincing.

McDonald and his collaborators first noticed the change eight years ago, when they kept needing to recalibrate the automated song detectors used to track blue whales off the California coast. The detectors are triggered by songs that match a particular waveform. Every year, McDonald had to set them lower.

Since then, he and Scripps Institution of Oceanography researchers Sarah Melnick and John Hildebrand have gathered thousands of blue whale recordings made since the 1960s, spanning populations from the North Atlantic to the South Pacific to the East Indian Ocean. Their analysis, published in October in Endangered Species Research, shows that the songs’ tonal frequency is falling every year by a few fractions of a hertz.

-- Wired @ http://www.wired.com/wiredscience/2009/12/blue-whale-song-mystery/

Here's a graph of the tonal frequency decrease since the 1960s:



The shift is appearing across all the geographical groups, but note that Blue Whales off the coast of California have decreased the pitch of their songs by 31 percent since the 1960s.
:wow:



Here's the abstract of the study:
http://www.int-res.com/abstracts/esr/v9/n1/p13-21/
And here's the fully study (PDF required) as published in ESR:
http://www.int-res.com/articles/esr2009/9/n009p013.pdf

[LakeSamish706]

1. Maybe they are doing a count down to end times! n/t

[Ignis]

3. "twoooooooooo ohhhhhhh onnnnnnnnnne twoooooooooo"

:scared: ;)

[MNDemNY]

2. The availability of tax free cigarettes in Tonga.

[existentialist]

4. Maybe they're suffering depression.

[anarch]

6. maybe they're getting angrier every year

[Ghost Dog]

49. Thought so too. They are sad

and maybe angry.

[Ignis]

53. Sad about their environement, perhaps, but ...

One factor the study looked at was the increase in blue whale populations as they recover from whaling. The hypothesis was that more males means more sexual competition, so they had to increase their pitch range to compete for the ladies.

I'm calling it the Barry White Defense. ;)

[rcrush]

5. They are waiting for that spaceship from Star trek 4.

[Aviation Pro]

7. They're calling out to their mothership....

...which will proceed to pummel the Earth with sonic pulses that will shake the foundation of the planet's crust. Then Jim Kirk and the rest of the original crew will travel back in time to pick up a couple of whales so that they can communicate with the mothership and prevent the destruction of mankind.

Oh, wait.

[walldude]

56. LOL.. I knew some other nerd would beat me to the punch...

:toast:

[sui generis]

8. is it the same mature whale population or new whales maturing

with different vocal attributes?

[Ignis]

16. Given the date range, we're looking at new whales as well.

Another explanation involves the recovery of blue whale populations, which were nearly hunted to extinction during the first half of the last century. It’s only since hunting ceased that they’ve been recorded. Maybe songs were higher-pitched when recording started, because the whales had to sing extra-loud in order to reach their scattered brethren. Now that there are more, they can lower their voices and their pitch.

But even in populations that escaped the carnage relatively unscathed, where population densities have remained steady, songs are getting lower.

“That’s the first place to look for an answer, but it doesn’t fit more-localized patterns. The population of blue whales off the U.S. west coast hasn’t shown a dramatic upwards trend in numbers, but its pitch is declining,” said Calombokidis.

[FirstLight]

9. Has anyone looked at Naval Sonar testing?

Perhaps they are singing lower to differentiate between themselves & the artificial sonar from human interference?


just a thought...need to study more on this

[justabob]

13. I was thinking something along those lines too

though not just the sonar stuff. I was thinking just noise pollution in general ... ship screws etc in the water. Perhaps they have to go to a lower note to be heard. I don't know. That was just the first thought off the top of my head.

[Ignis]

14. The article discusses noise pollution:

According to McDonald, the first explanation to come to mind involved noise pollution caused by increased shipping traffic. Ambient ocean noise has increased by more than 12 decibels since the mid-20th century. But if whales were trying to be heard above the din, they’d sing at higher rather than lower pitches, said McDonald.

That was also my first thought--thought I didn't know about the 12-dB increase. :wow:

[justabob]

interesting

ambient ocean noise up by 12 decibels? damn

:wow: is right!

[Ignis]

22. That's quite a jump.

I need to do more research on where/when/how the ambient increase occurs, to see if it's really 12dB on an average day, or if seasonal shipping skews that statistic.

Either way, that's a lot of noise to shout over.

[justabob]

23. indeed

I wish I knew more about this kind of thing. After your last post about actually needing to go to a higher range and sing louder to be heard, elephants popped into my head. Don't elephants communicate via super low frequencies to be heard over long distances? Is it different in the water? (I am not meaning to necessarily compare elephants and whales, just trying to remember the science of sound waves :) )

[Ignis]

26. Yes, you're absolutely correct about infrasound.

Here's a great link on the subject from Cornell's Ornithology department (long story):
http://www.birds.cornell.edu/BRP/elephant/Sections/dictionary/infrasound.html

I just don't know how much water changes the persistence/range of infrasound. :shrug:

[justabob]

30. thank you

I will check it out

[get the red out]

21. That would make sense

Avoid the interference, like shouting over noise to be heard by another person.

[eppur_se_muova]

43. Sonar is mostly ultrasonic. Diesel engine noise is the main worry, AFAIK. nt

[Ignis]

46. You are correct.

Diesel engines are producing most of the low-frequency ambient noise that falls into the normal pitch range of blue whales' songs (10 to 100 Hz frequency band).

Whether or not sonar is a factor, it wasn't included in this particular study.

[Stevenmarc]

10. Maybe they're getting into Barry White

[a la izquierda]

12. beat me to it...rats.

[NickB79]

27. Maybe that will help rebuild the population faster

:evilgrin:

[RedCappedBandit]

11. Maybe they're getting depressed due to the distruction of their habitat. nt

[Javaman]

15. Maybe the need to cut back to only a pack a day. nt

[MilesColtrane]

17. "Blue Whales...have decreased the pitch of their songs by 31 percent since the 1960s."

Just like Robert Plant!

[Ignis]

52. He sure doesn't screech like he used to.

I miss a good circa 1970 Plant waaaaaaaaaaaaaaaail. :smoke:

[juno jones]

18. Their song is stuck in their throat.

Just as Carlin observed in pigeons, it's happening to whales.

And the oil slick thing isn't as funny anymore either.

[Codeine]

19. They're in their Goth Phase.

Doing the whole Sisters of Mercy thing, painting their fins black, piercing their blowholes -- they'll grow out of it.

[Ignis]

20. Peter Murphy? Nah, maybe it's just a fluke.

:hide:

[bread_and_roses]

24. maybe it's a song of sorrow - we are poisoning their realm, after all (n/t)

[FirstLight]

25. +100

...so sad to me that there are more people who would rather joke about these things than attempt to understand that these creatures are ancient and may carry some inherent knowing.

Mass beachings, population and breeding issues, lower pitch in songs, ...if we knew what their language was, maybe we would have heard them warning us decades ago...

:( we are the proverbial frogs in the pot of boiling water, and we are partying like we are in a hot tub!

[Ignis]

31. The increasing frequency of beachings...

--especially mass beachings--also concerns me greatly.

Obviously, we don't have a complete historical record to compare against, but at least in terms of written history, these mass beachings are unprecedented.

But you can't fault people for making the obvious Barry White joke. ;)

[Cirque du So-What]

28. The lower the frequency of a sound, the farther it travels in water

Perhaps it's necessary for them to try establishing contact with farther-flung potential mates or to compensate for increasing levels of pollutants in the water (I'm guessing here).

[Ignis]

33. I've studied infrasound in elephants...

But my physics isn't up to snuff enough to completely understand the implications under water.

See this quote from the article:

"According to McDonald, the first explanation to come to mind involved noise pollution caused by increased shipping traffic. Ambient ocean noise has increased by more than 12 decibels since the mid-20th century. But if whales were trying to be heard above the din, they’d sing at higher rather than lower pitches, said McDonald."

Now, that struck me as odd, because I don't see why they'd try to sing higher when deeper sounds carry farther.

But if you read the full study, here's an explanation of what band is being overlapped by commercial shipping:

The dominant
low frequency noise in the deep-water northeast
Pacific is due to commercial shipping traffic, which
occurs primarily in the same 10 to 100 Hz frequency
band as blue whale songs. In the northeast Pacific, an
approximate 12 dB increase in ambient noise is
reported for the past 4 decades (Andrew et al. 2002,
McDonald et al. 2006b).

And here's the reason why the researchers discarded this hypothesis:

A lowered fundamental frequency in the band near
20 Hz would not significantly lower the intrinsic attenuation
of these acoustic signals, as spreading loss far outweighs
signal attenuation at all practical propagation
distances (e.g. 0 to 1000 km). Likewise, a change of a
few Hz would not substantially shift the blue whale signal
relative to ambient noise (McDonald et al. 2006b). A
lowered fundamental call frequency is predicted to result
in lower blue whale call source levels (see Supplement
3), counter to the expectation that call source levels
would increase to compensate for increased noise.
The frequency shift plot looks nearly linear in frequency
and time. This is not the relationship to be expected
if the animals were shifting away from a linear
increase in ambient noise, as it becomes exponentially
more difficult to physiologically shift down 1 Hz as the
frequencies become lower (Eq. S1). A quantitative assessment
of the likely non-linear increase in sound
source level to compensate for increased masking noise
is a complex topic (Gelfand 2004). While ambient noise
increase in the world’s oceans may be an important factor,
it appears not to be the dominant factor, as the expected
frequency shift owing to increasing noise would
be up rather than down.

Any thoughts? :hi:

[LeftyMom]

29. Puberty. nt

[Ignis]

34. They'll start growing hair in strange places, next.

[AngryAmish]

32. There are fashions in whale culture.

Low singing is just more popular nowadays. Like rockabilly.

[Odin2005]

35. Cultural trend in blue whale society?

But that would make to much sense to the deluded people who wish to deny the intelligence of these creatures.

[Ignis]

36. It's becoming increasingly difficult to deny, isn't it?

:hi:

You might like this article:
http://www.wired.com/wiredscience/2009/06/whalepeople/

It's a bit breezy, but it contains many links to some great research.

[Odin2005]

37. Wonderful article!

On a related note, I suggest you read "Songs of the Gorilla Nation", the autobiography of the high-functioning autistic ape researcher Dawn Prince-Hughes. She talks a lot about how intelligent our ape cousins are and actually refers to them as "people".

[Ignis]

39. Thanks!

I'll add that book to the list. ;)

I had to take a break from reading primate-related books after finishing A Primate's Memoir by Sapolsky recently. Amazing book, but alarming and depressing at the core. Still, highly recommended.

http://www.amazon.com/Primates-Memoir-Neuroscientists-Unconventional-Baboons/dp/0743202414

[amborin]

45. that's quite an article; very sad and also fascinating!

[amborin]

38. fascinating! i'm afraid to read the study, what is its executive summary?

[Ignis]

40. Sadly, we don't know what's causing it.

None of the hypotheses tested were conclusively proven. The best they could do was record the data and point out promising avenues of research for the next study someone undertakes in this area.

From the abstract:

Any behavioral, ecological, oceanographic or anthropogenic change hypothesis seeking to explain the observed shifts should account for the worldwide occurrence of a nearly linear downward shift in the tonal frequencies of blue whale song. Hypotheses examined consider sexual selection, increasing ocean noise, increasing whale body size post whaling, global warming, interference from other animal sounds and post whaling increases in abundance. None of the commonly suggested hypotheses were found to provide a full explanation; however, increasing population size post whaling provides an intriguing and testable hypothesis that recovery is altering the sexually selected tradeoff for singing males between song amplitude (the ability to be heard at a greater distance) and song frequency (the ability to produce songs of lower pitch).

[amborin]

42. my fear is it's due to something really ominous

[Ignis]

55. How ominous, exactly?

[Fire_Medic_Dave]

41. Age?

[librechik]

44. hormones in the water from spill?

guess..

[Ignis]

47. The study did look into increasing oceanic acidity

But there's nothing conclusive there. :shrug:

[librechik]

51. well.if the songs are like foreplay for mating--maybe the females said "lower, lower."

heh

[cherokeeprogressive]

48. Puberty?

[TexasObserver]

50. Because to sing the blues, you gotta live the blues.

[harun]

54. Maybe the change is due to the change in the composition of the medium

the sound is traveling through.

I guess if that was the case we would see this change in recordings of all sounds in the Ocean though. Wonder if it is seen in any other animals.