Editing Indri (section)

=== Communication ===
{{listen
| type     = sound
| filename = Roep Indri Indri.ogg
| title    = Indri duet
| description = The wailing "song" of the Indri
}}
[[Image:Iiv AGrandidier 1204.jpg|right|thumb|229px|Drawing by [[Alfred Grandidier]]]]
The indri makes loud, distinctive songs, which can last from 45 seconds to more than 3 minutes. Song duration and structure varies among and even within groups, but most songs have the following three-phase pattern.<ref name=Pollock>{{Cite journal|last=Pollock|first=Jon I.|date=June 1986|title=The song of the Indris (Indri indri; Primates: Lemuroidea): Natural history, form, and function|journal=[[International Journal of Primatology]] |volume=7|issue=3|pages=225–264|doi=10.1007/BF02736391 }}</ref>

Usually, a roaring sequence lasting for several seconds will precede the more characteristic vocalizations. All members of the group except the very young participate in this roar, but the song proper is dominated by the adult pair. They follow the roar with a long note sequence, characterized by notes of up to five seconds in duration. After this is a descending phrase sequence. The wails begin on a high note and become progressively lower-pitched. It is common for two or more indri to coordinate the timing of their descending notes to form a duet.<ref name=Pollock/>

Different indri groups typically sing sequentially, responding to one another. As well as solidifying contacts between groups, the songs may communicate territorial defense and boundaries, environmental conditions, reproductive potential of the group members, and warning signals.<ref name=Pollock/> The indri may sing after disturbances such as thunder, airplanes, bird calls, and other lemur calls.<ref name=Quinn /> A group will sing almost every day, up to seven times daily. The peak singing hours are between 7 and 11 am. Daily frequency of song is highest during the indri's breeding season from December to March.<ref name= "Glessner">{{cite journal |last1=Glessner |first1=Kellie D. G. |last2=Britt |first2=Adam |title=Population Density and Home Range Size of Indri indri in a Protected Low Altitude Rain Forest |journal=International Journal of Primatology |date=August 2005 |volume=26 |issue=4 |pages=855–872 |doi=10.1007/s10764-005-5326-2 }}</ref>

Several other indri vocalizations have been identified. The "roar" is also used as a warning signal for aerial predators such as hawks.<ref name=Quinn /> The indri emit a "hoot" or "honk" to warn of terrestrial predators such as the [[Fossa (animal)|fossa]]. Other vocal categories include the "grunt", "kiss", "wheeze", and "hum". The purpose of these is not well understood.<ref name=PowzykThalmann2003 />

Before singing, the indri move to the tree tops, which allows them to be heard up to 4&nbsp;km away.<ref name= "Giacoma">{{cite journal |last1=Giacoma |first1=Cristina |last2=Sorrentino |first2=Viviana |last3=Rabarivola |first3=Clement |last4=Gamba |first4=Marco |title=Sex Differences in the Song of Indri indri |journal=International Journal of Primatology |date=August 2010 |volume=31 |issue=4 |pages=539–551 |doi=10.1007/s10764-010-9412-8 }}</ref>