Communication: Listening in
Many vertebrate species communicate with sounds. These sounds can range from simple innate calls, such as monkey alarm calls, to complex sequences of sounds that need to be learned, such as bird song and human speech. However, it has been challenging to study these more complex sounds under natural conditions because, for many years, recording technology has not been good enough to record multiple animals at once. Thus, researchers often resorted to using a combination of a single microphone and constant visual observation to study one, two or three animals at a time.
Now, in eLife, Lisa Gill, Wolfgang Goymann, Andries Ter Maat and Manfred Gahr of the Max Plank Institute for Ornithology report how backpacks containing miniature wireless microphones can be mounted onto the backs of zebra finches and then used to listen in as these songbirds interact with each other (Gill et al., 2015). A typical zebra finch is the size of a mouse and weighs about 15 grams, so the backpack had to be light and attached in way that did not prevent the bird from flying or copulating. The backpack, which weighed about 1 gram, was attached so that the microphone faced the animal, whereas the antenna that sent the signal to the recording apparatus pointed away from the bird (see image). The Max Planck team also developed software that automatically categorizes vocal interactions between two or more animals.
Prior to this study, the best way to record multiple animals in the same location was to use an array of microphones, followed by sophisticated sorting software to identify which animals were vocalizing, as was recently done with mice (Neunuebel et al., 2015). Last year Alexei Vyssotski and co-workers in Moscow and Zurich used microphones attached to zebra finches for the first time (Anisimov et al., 2014): however, the data were stored on a chip in the backpack, and had to be manually uploaded to a computer later, rather than being transmitted to the computer wirelessly in real time as done by Gill et al.
The subsequent experiment designed by Gill et al. is reminiscent of a reality television show. Imagine having a group of single young men living in a house for an extended period time, and a group of single young women living in a different house. Then select four of the men and four of the women, attach wireless microphones to them, move them to a large house in the tropics with four bedrooms, and record every word they say for 20 days. This is what was done with the birds, except that the house was a large, hot and humid aviary, and the rooms were nest boxes, provided with nest material nearby. No rules were enforced on the animals, so they were free to wander, socialize, mate and fight as they wished.
Gill et al. found that the communications between the birds changed over the course of the 20 days, partly depending on who paired with whom. At first all the birds produced a flurry of long distance calls, and each bird responded a lot to all other birds. After several days, as soon as they found the nest material, individual birds started to form opposite-sex pairs, communicating with each other much more (by a factor of five or six) than with the other birds. The birds in a pair also tended to use ‘cackle and whine’ calls to communicate with each other, but not with other birds. ‘Tet’ calls were produced more often by males during unpaired and non-nesting social contexts, whereas ‘stack’ calls were produced more often by females during unpaired and nest defense contexts.
A remarkable finding was that after 15–20 days, the male–female pairs that used the same call types to communicate with each other were more successful in laying and incubating eggs. Those that communicated more often with different call types were unsuccessful mates. These findings indicate that proper communication is important for forming successful pair bonds and producing offspring, and show that there is more to the chatter of birds than randomly produced calls.
Relatively few animals are capable of vocal learning: those that are include songbirds, parrots, hummingbirds, humans, bats, elephants, dolphins and seals (Petkov and Jarvis, 2012). In zebra finches, as in many other songbirds that live in temperate climates, males have the ability to learn how to produce novel vocalizations, whereas females have lost the this ability (Odom et al., 2014) for both song and calls (Simpson and Vicario, 1990). However, the results of Gill et al. could mean that although female zebra finches cannot imitate new sounds, they still learn when and where to produce their innate sounds through social learning.
The results of the Max Planck team might stimulate further research on other species that vocalize, including non-human primates such as marmosets, macaques and chimpanzees: both the males and females of these species can only produce innate vocalizations but, like female zebra finches, they are capable of learning when and where to produce these sounds through social experience (Petkov and Jarvis, 2012; Takahashi et al., 2015). In the long term this combination of wireless technology and sophisticated software may help us learn more about the rules that govern vocal communication in animals.
References
-
Reconstruction of vocal interactions in a group of small songbirdsNature Methods 11:1135–1137.https://doi.org/10.1038/nmeth.3114
-
Female song is widespread and ancestral in songbirdsNature Communications 5:3379.https://doi.org/10.1038/ncomms4379
-
Birds, primates, and spoken language origins: behavioral phenotypes and neurobiological substratesFrontiers in Evolutionary Neuroscience 4:12.https://doi.org/10.3389/fnevo.2012.00012
-
Brain pathways for learned and unlearned vocalizations differ in zebra finchesJournal of Neuroscience 10:1541–1556.
Article and author information
Author details
Publication history
Copyright
© 2015, Jarvis
This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 960
- views
-
- 86
- downloads
-
- 0
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Further reading
-
- Developmental Biology
- Ecology
Organisms require dietary macronutrients in specific ratios to maximize performance, and variation in macronutrient requirements plays a central role in niche determination. Although it is well recognized that development and body size can have strong and predictable effects on many aspects of organismal function, we lack a predictive understanding of ontogenetic or scaling effects on macronutrient intake. We determined protein and carbohydrate intake throughout development on lab populations of locusts and compared to late instars of field populations. Self-selected protein:carbohydrate targets declined dramatically through ontogeny, due primarily to declines in mass-specific protein consumption rates which were highly correlated with declines in specific growth rates. Lab results for protein consumption rates partly matched results from field-collected locusts. However, field locusts consumed nearly double the carbohydrate, likely due to higher activity and metabolic rates. Combining our results with the available data for animals, both across species and during ontogeny, protein consumption scaled predictably and hypometrically, demonstrating a new scaling rule key for understanding nutritional ecology.
-
- Ecology
Advances in tracking technologies have revealed the diverse migration patterns of birds, which are critical for range mapping and population estimation. Population trends are usually estimated in breeding ranges where birds remain stationary, but for species that breed in remote areas like the Arctic, these trends are often assessed in over-wintering ranges. Assessing population trends during the wintering season is challenging due to the extensive movements of birds in these ranges, which requires a deep understanding of the movement dynamics. However, these movements remain understudied, particularly in the mid-latitudes, where many Arctic breeders overwinter, increasing uncertainty in their ranges and numbers. Here, we show that the Arctic breeding raptor Rough-legged buzzard, which overwinters in the mid-latitudes, has a specific wintering strategy. After migrating ca. 1500 km from the Arctic to mid-latitudes, the birds continue to move throughout the entire over-wintering period, traveling another 1000 km southwest and then back northeast as the snowline advances. This continuous movement makes their wintering range dynamic throughout the season. In essence, this movement represents an extension of the quick migration process, albeit at a slower pace, and we have termed this migration pattern ‘foxtrot migration’, drawing an analogy to the alternating fast and slow movements of the foxtrot dance. These results highlight the potential errors in range mapping from single mid-winter surveys and emphasize the importance of this migration pattern in assessing the conservation status of bird species. Understanding this migration pattern could help to correctly estimate bird populations in over-wintering ranges, which is especially important for species that nest in hard-to-reach regions such as the Arctic.