One for all and all for a sparrow! [Thesis]

Passereau - Alert Launcher - 2021 - 

In the 1937 cartoon Snow White and the Seven Dwarfs, when she finds herself in the dwarfs' house faced with an abominable mess, Snow White calls out to the animals of the forest with an interspecies melody (a whistle) understood by several species, to help her bring order to the cottage. 

When faced with a crisis situation, such as during an assault, we call for help by shouting while we seek to fend off our attacker. In some cases, witnesses will avoid interfering and in others a few sentient beings will step in to assist us.

What if, like Snow White, we could solicit other species to assist us? Imagine, then, an intra and interspecific cry to which rodents, cats, pigeons and dogs will respond in unison by running to our aid to repel the intruder. We could believe ourselves in a fairy tale ... And if this phenomenon was not so supernatural as that?

This phenomenon can be observed in some birds that in the presence of a predator emit a harassment call recruiting birds of its species as well as others to harass the predator in group in order to make it flee.

But how do these intra  and interspecific communications take place? On what is this communication based?  Is this type of communication frequent? This is what Mylène Dutour proposes to discover in her thesis "Communicating between species to cope with the predator: the case of harassment calls in passerines".

Why read this thesis

Mylène Dutour invites us, with passion, to discover the theme of communication between passerine species in defense processes by harassment. It is around this central subject that she develops her research approach and results in a thesis-article format. This choice makes sense thanks to the work put in place to maintain a clear, fluid narrative thread that offers the reader the pleasure of discovering research in behavioral ecology.

Echoing her subject, the researcher manages to bring together various disciplines such as bioacoustics, behavioral biology, ecology and physiology, but also her own talents as a photographer and artist to unveil the mysteries of her subject. Thus, she succeeds in capturing our attention and growing our interest throughout the manuscript by accompanying us and cross-referencing her observations to those of her peers.

Excerpt - foreword

This thesis work corresponds to the succession of different personal and intellectual histories. 
My work on the study of stalking behavior began in Master 2, or perhaps it had already taken root in Master 1 during my internship on communication in the little owl (Athene noctua) under the supervision of Thierry Lengagne.

After obtaining some very nice results dealing with the impact of the European owl on the harassment behavior of passerines, I had the chance to pursue this work in a thesis. [But here we are, the ideas and questions were flowing... So, how to tell the reader a homogeneous story since this thesis work is articulated around several questions? The desire to learn and to discover knowledge did not weary me during these three years. And, on the contrary, it is partly my fault if some results deviate from the initial path. It must be said that 36 study models lent themselves particularly well to this aspect!

 Finally, our questions were diverse and varied, but they were above all complementary and centered around the same anchor point. This thesis is therefore structured in three sections: the first one sets the theoretical framework, the second one includes the published, accepted or in preparation articles and the third one corresponds to the general discussion.

I wanted to offer the reader throughout this manuscript a complete story revolving around one main theme, communication between passerine species in the case of predator harassment.

Bringing the bell 

The sum of Mylène Dutour's publications is impressive and full of results on her subject. Nevertheless, one of the most amazing is the application of this research to develop tools and study methods for conservation biology. 

Conservation biology is the field studying the living world and its biological diversity: biodiversity, with the aim of protecting it. One of the key measures of conservation biology is the determination of species range and population size. Through her research, Mylène Dutour proposes the use of passerine harassment calls as a complementary tool to the acoustic population study of the European owl. This method provides three levels of information: 

•  Validating the presence of European owls in an environment: Indeed, the use of passerine alarm calls creates a positive response from a set of other species when the predator is present in that territory and a negative response when it is absent. This method of indirect detection has validated the presence of predators in a region of Ain as well as the false absences found by traditional methods. 

• Estimate the density of species of an environment: This method, by its call effect, also allows to estimate the density and diversity of species of a given environment by censuses after the emission of the harassment call. 

• Estimating the quality of an environment : The intensity of the harassment response following the calls is also information on the quality of the environment: unmanaged forest with denser and more diverse communities; young managed forests with less diversity and less density. 

However, the author warns about the negative effect of an overuse of these harassment calls that can lead to a desensitization of the community to this call.

Unity is strength

Mylène Dutour's work shows us how species cooperate in spite of their differences in the face of a common aggressor. We can see all the complexity of the networks revolving around a simple bird call. The results obtained, in addition to helping us to better understand this process, also lead to tools for studies in conservation biology.

This research work reminds us that communication is not unique to humans and that mutual aid is a survival strategy used by many species of living beings. Overcoming the limits of their species and language, these birds unite in true community to become David against Goliath.

The luckiest among us are fortunate enough to be able to listen to nature by simply opening their window. However, it would seem that we have trouble hearing some of the cries of alarm, distress or mutual aid from members of our own species, and in some cases, our own cries...

Good reading

This work was defended on November 28, 2018 in Lyon at the doctoral school Evolution, Ecosystems, Microbiology, Modeling : ED 341  of the Claude Bernard Lyon 1 University within the Laboratory of Ecology of Natural and Anthropized Hydrosystems (EHNA) (Lyon - France) 

Sources

Mylène Dutour. Communicating between species to cope with the predator: the case of harassment calls in passerines. Ecology, Environment. University of Lyon, 2018. French. NNT: 2018LYSE1251. tel-02426002v2

Credit citation: Figure 3: Harassment calls made by black-capped chickadees (Thesis)

Thesis: https://theses.hal.science/tel-02426002/

PDF: https://theses.hal.science/tel-02426002v2/document