The Audible Phylogeny of Lemurs (in-progress) will be a two-part work presentable as a single continuous piece or as a pair of shorter pieces. It is the product of three years of research on prosimian primates, including work in residence at the Duke University Lemur Center, where I have had the privilege to observe and record semi-free range lemurs and to conduct a set of playback studies. The Duke Lemur Center is the world's largest lemur reserve outside of Madagascar, housing 250 or so highly charismatic animals, many of them in generous, forested natural habitat enclosures. This work would not be possible without the DLC and its knowledgeable staff and care technicians.

The piece is largely based on a 1994 study by Joseph Macedonia and Katherin Stanger, in which the authors evaluated communication evidence—primarily vocal signal information—to produce a lemur phylogeny (analysis of species relationships). Comparing the Macedonia-Stanger study to a more recent molecular phylogeny (see below), I was struck by how well the earlier communication-based analysis held up—excellent news for an artist interested in animal communication. It suggests that, with proper context, the evolutionary story encoded in the vocalizations of modern animals is audible.

Part I, presented here, deals primarily with affiliative calls and a few mild agonistic calls and group alerts—i.e. calls associated with social interaction (as opposed to the alarms, advertisement calls, and more extreme agonism, to be dealt with in Part II). About 12 different species are represented, although Lemur catta (the familiar ring-tailed lemur) and the closely related Hapalemur griseus are the most prominently featured. My goal is to preserve and augment the calls' natural characteristics and to group and combine them so as to explicate relationships between calls of different species, making the phylogeny audible and the beauty and complexity of the calls accessible. You cannot simply pull up a chair at the Duke Lemur Center and hear these relationships unfold! The piece is assembled from many hours of recordings—a grunt here, a mew or wail there, occasionally a "scene." The vocalizations are documented for context of emission, cross-referenced with the scientific literature, and meticulously cleaned, enhanced, edited, and spatialized to reveal their acoustic structures and phylogenetic relationships. In several cases, I have used my own observations to augment or extrapolate from the literature, resulting (hopefully) in original insights on the relationships between calls (see Sections IV and V).

I am deeply indebted to biologist Joseph Macedonia for his guidance and input throughout this project; his authoritative work on lemur vocalization is the basis for this piece.

1:56 Section II—Mild agonism: Submissive/defensive calls across four species

Species, in order of prominence:

Propithecus coquereli

Eulemur macaco flavifrons

Lemur catta

Varecia variegata rubra

As the arousal level in Section I reaches fever pitch, the scene changes abruptly. The outlier of Section I Propithecus coquereli becomes the focus of Section II, a comparison of calls emitted in contexts of mild agonism. The vocalizing animal acknowledges the higher rank of another, while simultaneously signaling its willingness to defend itself. [Rough translation: "OK, OK...but don't push me."] P. coquereli dominates a duet of sorts with Eulemur macaco flavifrons. Lemur catta and Varecia variegata rubra appear intermittently.

As in Section I, the listener can hear how even distantly related species share acoustically similar vocalizations emitted in similar contexts.

0:00 Section I—Grunt homology across eight species, with increasing arousal

Species, in order of appearance:

Lemur catta

Hapalemur griseus

Eulemur mongoz

Eulemur rubriventer/Eulemur coronatus

Eulemur macaco flavifrons

Varecia variegata rubra

Propithecus coquereli

Many lemur species emit grunts in low-arousal contexts. In this section, I have chosen a "path" through the phylogeny that allows the listener to hear the relationships between grunts of different species. The section opens with the single-click grunt of Lemur catta. Next, we hear the double-click grunt of Hapalemur griseus, the species most closely related to L. catta. Next is the three-to-five-click grunt of Eulemur mongoz, followed by more species in the Eulemur genus. The section works its way out to distantly related species.

The section shows another angle on grunts: Throughout the section, the animals overall are becoming increasingly aroused. This demonstrates additional relationships between grunts. For example, as L. catta and H. griseus become increasingly aroused, they begin to emit click series, which sound like slowed-down versions of multiple-click Eulemur grunts, and also resemble the long growl of the distantly related Varecia species. As Eulemur and other species become more aroused, they begin to emit snorting and sneezing sounds, which resemble high-arousal barks and alerts of other species. These expulsive vocalizations will be further explored in Section VI.

8:23 Section VIII—Close contact calls in three species with light rain and jet flyover

Species, in order of appearance:

Lemur catta

Hapalemur griseus

Propithecus coquereli

This section superimposes four separate scenes, each of which features close contact vocalizations. Once again, the close relationship of L. catta and H. griseus is the focal point. The dominant scene is that of a group of ringtails grooming in the shelter of trees—a light rain taps on the leaves, a jet passes overhead, and a group of ringtails in the distance are calling in alarm. The ringtails in the foreground call out quietly to one another and emit "hmms," which are low-amplitude close contact calls. Superimposed on this scene is a lone ringtail emitting a quavered version of the "hmm" call. Also superimposed, a pair of H. griseus emit their own "hmms" and light clear calls inside a carrier. Finally, toward the end (announced by a sudden onset of cicada chorus), a single P. coquereli, once again acting as an outlier, emits a close contact call that resembles, structurally and contextually, the quavered version of the L. catta's "hmms."

2:41 Section III—Contact calls across four species, with increasing arousal

Species, in order of appearance:

Lemur catta

Hapalemur griseus

Eulemur coronatus

Propithecus coquereli

Section III begins with a flurry of activity—this material derives in part from the results of a playback study, in which I played ringtails a set of moderately digitally processed contact calls. After a series of chirps in response to the playback, the section settles into a relatively calm comparison of low-arousal tonal contact calls. As in Section I, the comparison proceeds from L. catta to the closely related H. griseus to a representative of the Eulemur species, E. coronatus; once again, P. coquereli is the outlier, appearing toward the end of the section as the other species are reaching high arousal.

Also as in Section I, the animals' overall arousal levels intensify throughout. As their arousal levels increase, they introduce modulation into their calls, which become warbled or distorted.

4:18 Section IV—Call concatenation under moderate-to-high arousal conditions in Hapalemur griseus and Lemur catta

Hapalemur griseus concatenation 4:18

Hapalemur griseus and Lemur catta intertwined 4:36

Hapalemur griseus and Lemur catta simultaneously 4:50

I will confess that, vocally at least, H. griseus is my favorite lemur species. The eerie combination of their "angry baby" calls with their aggressive personalities and outraged facial expressions make them one of the joys of working at the DLC.

Among my favorite H. griseus vocal behaviors is that of juxtaposing seemingly disparate vocalizations into concatenations that tempt the researcher (who definitely knows better) to use words like "syntax." These concatenations occur most frequently in contexts of moderate arousal (such as later-than-usual provisioning or in response to the alarms of another species). This section begins with a series of these strands edited together into a composite that gives a sense of H. griseus's vocabulary and combinatorial tendencies.

Similarly, I have observed that ringtails (L. catta) in moderate-to-high arousal situations (such as boundary encounters with conspecifics at the DLC) will exhaust half or more of their vocal repertoire in a matter of a few minutes. L. catta's concatenations come much more slowly than H. griseus's and are more likely to be distributed among several members of a group—but the impression of a rapid-fire cataloging of a large portion of the species' vocabulary is similar. Thus, the section proceeds by first intertwining the concatenations of these closely related species, and finally by comparing them as simultaneous strands.

5:13 Section V—Moderate distance contact calls with rising tonal elements, across six species

Species, in order of appearance

Hapalemur griseus

Eulemur coronatus

Varecia variegata rubra

Eulemur fulvus

Eulemur rubriventer

Several lemur species use calls with rising tonal elements for moderate-distance contact functions. The section is introduced by the "boing" of H. griseus, a call we have heard repeatedly in the previous section. This call is then compared to the mew of V. variegata rubra and the rising grunt of E. coronatus. As the section continues, the rising grunts of several other Eulemur species are introduced.

5:40 Section VI—Single- and double-unit expulsive calls

Species, in order of appearance:

Daubentonia madagascariensis

Varecia variegata rubra

Propithecus coquereli

Lemur catta

The entire section is underscored by the double-unit "sneeze" call of the aye-aye (Daubentonia madagascariensis), the most "distant" outlier of the entire piece (see phylogenies above). Initially, the aye-aye's "sneeze" is compared to the "growl-huff" of another outlier, V. v. rubra. Next it is compared to the very similar double-unit "shee-fak" call of P. coquereli. As the "shee-faks" increase in intensity, L. catta "plosive barks" and Eulemur "snorts" enter as accents to the texture. All of these calls have in common a strong expulsive quality, with significant nasal contribution, and contextually they share a moderate-to-high level disturbance function.