Category Archives: migration

Satellite Telemetry Uncovers the Tracks of Tiny Ocean Giants

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Pygmy Blue Whale

The pygmy blue whale, cousin to the more well-known Antarctic blue whale, has an enigmatic history. Pygmy blue whales dwell in vast expanses of the Indian and southern Pacific oceans, and are a highly mobile species. The species was identified in 1966—although it’s likely to have been confused with its cousin the “true” blue whale prior to 1966—so it’s only in recent years that we’ve been able to catch glimpses of these elusive cetaceans during their migrations to and from breeding and feeding grounds. The researchers of a recent PLOS ONE paper tested out a new method of tracking these whales: satellite telemetry (described below). Using this method, the researchers mapped the migration of pygmy blue whales as they moved from the coast of Australia to the waters of Indonesia. We caught up with author Virginia Andrews-Goff to get some additional details on what it’s like to track these tiny giants.

How did you become interested in pygmy blue whales, and how did you get involved in mapping their migratory movements?

This research was carried out by the Australian Marine Mammal Centre, a national research centre focused on understanding, protecting and conserving whales, dolphins, seals, and dugongs in the Australian region. The work we carry out aims to provide scientific research and advice that underpins Australia’s marine mammal conservation and policy initiatives. We, therefore, have a keen interest in all whales that migrate through Australian waters including pygmy blue, right and humpback whales.

Pygmy blue whales are of particular interest, however, as so little is known in regard to their movements and population status.  Large scale movements of whales are particularly hard to study and what we do know about pygmy blue whales we have mainly learnt from examining whaling records. Fortunately, pygmy blue whales were targeted by the whaling industry for only a very short period of time in the late 1950s and early 1960s just prior to the IWC banning the hunting of all blue whales in 1966.

What are the challenges of better understanding whale migration in general?

Large-scale, long-term whale movements are challenging to study as it is impractical to do so by direct observation. Therefore, we need to use devices, such as satellite tags, that can be attached to the whale to provide real-time location information.

What is satellite telemetry and how did it enable your findings?

In this case, satellite telemetry refers to the use of a satellite-linked tag attached to the whale. This tag communicates with the Argos satellite system when the antenna breaks the surface of the water. A location can then be determined when multiple Argos satellites receive the tag’s transmissions. We then receive this location data in almost real time via the Argos website, which allows us to track the movement of the tagged whale.

Pygmy Blue Whale 2

Based on your tracking, you found that the pygmy blue whales traveled from the west coast of Australia north to breeding grounds in Indonesia. Can you give readers a sense of why they travel this route?

Generally, whales migrate between productive feeding grounds (at high latitudes) in the summer to warmer breeding grounds (at low latitudes) during the winter. The exact reason for this general pattern is unclear, though quite a few theories exist, including to avoid predators, to assist the thermoregulatory ability of the calf, and to birth in relatively calm waters.  Because of the timing of this migration, we believe these animals travel to Indonesian waters to calve. Usually it is assumed that whales fast outside of the summer when no longer located in the productive feeding grounds. Interestingly, these pygmy blue whales travel from productive feeding grounds off Western Australia to productive breeding grounds in Indonesia and therefore, probably have the opportunity to feed (and not fast) on the breeding grounds.

Filtered satellite tag derived locations of pygmy blue whales (n = 11) by month.

Satellite tag derived locations of pygmy blue whales by month.

You’ve mentioned that pygmy blue whale migratory routes correspond with shipping routes. How does this interaction impact the whales?

Baleen whales (whales that use filters to feed instead of teeth) use sound for communication and to gain information about the environment they occupy. When pygmy blue whale movements correspond to shipping routes, there is potential for the noise generated by the ships to play some role in altering calling rates associated with social encounters and feeding.

Why is it important for us to better understand pygmy blue whale migration, and how does mapping their migratory movements help conservation efforts for this endangered animal?

Our coauthor, Trevor Branch, hypothesised in 2007 that pygmy blue whales occupying Australian waters traveled into Indonesian waters. However, prior to this study, we didn’t actually know that this was the case. As such, conservation efforts relevant to the pygmy blue whales that use Australian waters are required outside of Australian waters too. We can also now gain some understanding of risks within the pygmy blue whale migratory range, such as increased ambient noise from development, shipping, and fishing, and therefore assist in mitigating these risks.

What’s next for you and your research team?

A question mark still remains over the movements of the pygmy blue whales that utilise the Bonney Upwelling feeding grounds off southern Australia. Genetic evidence indicates mixing between the animals in the feeding areas of the Perth Canyon (the animals that were tagged in this study) and the Bonney Upwelling. This indicates the potential for individuals from the Bonney Upwelling to follow a similar migration route to those animals feeding in the Perth Canyon. However, it is also thought that Bonney Upwelling animals may utilise the subtropical convergence region south of Australia. We plan to collaborate on a research project that aims to tag the pygmy blue whales of the Bonney Upwelling and ascertain whether these animals move through the same areas and are therefore exposed to the same risks as the Perth Canyon animals.

Pygmy Blue Whale 3

We look forward to seeing more from Dr. Andrews-Goff and her team in the future. In the meantime, read more about the elusive worlds of southern Pacific Ocean whales here at the EveryONE blog.

Citation: Double MC, Andrews-Goff V, Jenner KCS, Jenner M-N, Laverick SM, et al. (2014) Migratory Movements of Pygmy Blue Whales (Balaenoptera musculus brevicauda) between Australia and Indonesia as Revealed by Satellite Telemetry. PLoS ONE 9(4): e93578. doi:10.1371/journal.pone.0093578

Image 1: IA19847 Blue pygmy whale

Photograph © Mike Double/Australian Antarctic Division

Image 2: IA19850 Blue pygmy whale

Photograph © Mike Double/Australian Antarctic Division

Image 3: pone.0093578

Image 4: IA19851 Blue pygmy whale off Western Australian coast near Perth, Western Australia, Australia Photograph © Mike Double/Australian Antarctic Division

The post Satellite Telemetry Uncovers the Tracks of Tiny Ocean Giants appeared first on EveryONE.

What Early Neolithic People Left Behind: Levantine Arrowheads Found in Saudi Arabia

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Palaeodeserts Project Crassard et al PLoS ONE 2013 Thinking about spending the summer in the sun and sand? Early Neolithic humans may have thought so too, although with more survival-oriented goals in mind. A recent study published in PLOS ONE suggests that early humans, who set up camp in the Eastern Mediterranean (about 10,000 BCE), may have traveled as far as Saudi Arabia in search of game and water.

In this study, researchers unearthed several types of Neolithic arrowheads in the northern peninsula of Saudi Arabia at the site of Jebel Qattar, which suggests a link between Neolithic people of the Levant—modern-day Jordan, Lebanon, Syria, Israel, Palestine, and Cyprus—to areas as far south as Saudi Arabia. Arrowheads and other tools are, by and large, the main type of early human artifact observable today prior to the introduction of pottery (about 7000 BCE), and are integral to our understanding of the people who created and used them. Tools and arrowheads types, like the ones discovered at Jebel Qattar, provide researchers with evidence of early technology used for hunting.

Beyond the Levant Image

Helwan points found at Jebel Qattar

Accurately identifying early Neolithic artifacts is a tough job—these arrowheads are over 10,000 years old, after all—and requires researchers to carefully sift out other objects uncovered during surface collection and trench excavations. In fact, the researchers discovered a total of 887 stone tools at the site of Jebel Qattar, only ten of which have been identified as Levantine types, known more specifically to researchers as El-Khiam and Helwan points. Named for their places of origin in Israel and Egypt respectively, the El-Khiam and Helwan arrowhead types are common to Levantine sites throughout the Neolithic period. This study, however, represents the first time archaeologists have discovered them in the Nefud Desert of Saudi Arabia.

Levant Map

Current understanding of early people living during the Neolithic period is rooted in excavation sites in the Levant and the larger area of the Fertile Crescent—the area in green on the map above—a geographical region containing parts of Western Asia, including the Levant, as well as parts of the Nile Valley and Nile Delta of northeast Africa. The Fertile Crescent is home to several major innovations, including the domestication of animals and the development of cereal, and is often known as the ‘cradle of civilization’. The discovery of El-Khiam and Helwan arrowheads in Saudi Arabia alludes to this hotspot of innovation and technology and suggests possible interaction between these early Neolithic peoples.

However, because so little evidence from the Neolithic period survives intact today, our understanding of Neolithic peoples is a work-in-progress. Nevertheless, tracing Neolithic people from the Levant as far as Saudi Arabia suggests that we may want to study broader areas when considering their trajectory. Of course, there is further exploration to be done beyond the borders of the Levant.

Citation: Crassard R, Petraglia MD, Parker AG, Parton A, Roberts RG, Jacobs Z, Alsharekh A, Al-Omari A, Breeze P, Drake NA, Groucutt HS, Jennings R, Re´gagnon E, and Shipton C . (2013) Beyond the Levant: First Evidence of a Pre-Pottery Neolithic Incursion into the Nefud Desert, Saudi Arabia. PLOS ONE 8(7): e68061. doi: 10.1371/journal.pone.0068061

Images: doi: 10.1371/journal.pone.0068061

How eels navigate to the Sargasso Sea

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The migration of European eels (Anguilla anguilla) between freshwater habitats in Europe and North Africa and their spawning ground in the Sargasso Sea is one of the unsolved mysteries in animal navigation. Scientists have speculated that the eels may use the Earth’s magnetic field as a guide during their 6000 kilometer trip, and an article published today by Durif et al. strongly supports this idea.

To test the ability of eels to orient using a magnetic field, the authors used a carefully controlled laboratory setting, in which they eliminated other potential orientation cues, including odors, vibrations, light, and sounds.  They also created an artificial magnetic field, the same strength as the Earth’s magnetic field, which could be oriented in different directions.  Turning the artificial magnetic field between test runs helped rule out the possibility of the eels using other orientation cues.

The authors found that the eels consistently oriented in a particular direction with respect to magnetic north and that the eel’s particular orientation varied with water temperature.  Below 12 oC, which is the temperature range associated with eel migration, the eels oriented in the direction they had been transported from the holding tank to the testing tank.  This also corresponded with the direction of increasing water temperature.  Above 12 oC, the eels oriented at right angles to the direction they had been transported, which the authors speculate might reflect foraging behavior during times of the year the eels are not migrating.

Thus, eels seem capable of using the Earth’s magnetic field as a navigational guide.  They also seem to integrate this information with other cues, such as water temperature, to determine their direction of movement.

While these results provide some insight into how eels navigate to their spawning ground, other mysteries about eel migration remain, including where the spawning ground in the Sargasso Sea is precisely located.  For further reading about eel migration, see another paper published in PLOS ONE in October, in which Béguer-Pon et al. tagged adult American eels (Anguilla rostrata) to map their migration to the Sargasso Sea but instead learned something about porbeagle shark predation.

Image credit: Steffen Zienert (http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=308)

Citations: Durif CMF, Browman HI, Phillips JB, Skiftesvik AB, Vøllestad LA, et al. (2013) Magnetic Compass Orientation in the European Eel. PLoS ONE 8(3): e59212. doi:10.1371/journal.pone.0059212

Béguer-Pon M, Benchetrit J, Castonguay M, Aarestrup K, Campana SE, et al. (2012) Shark Predation on Migrating Adult American Eels (Anguilla rostrata) in the Gulf of St. Lawrence. PLoS ONE 7(10): e46830. doi:10.1371/journal.pone.0046830