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This study extends recent research demonstrating that the veiled chameleon (Chamaeleo calyptratus) can produce and detect biotremors. Chameleons were paired in various social contexts: dominance (male–male; female–female C. calyptratus); courtship (male–female C. calyptratus); heterospecific (C. calyptratus + C. gracilis); and inter-size class dominance (adult + juvenile C. calyptratus). Simultaneous video and accelerometer recordings were used to monitor their behavior and record a total of 398 biotremors. Chamaeleo calyptratus produced biotremors primarily in conspecific dominance and courtship contexts, accounting for 84.7% of the total biotremors recorded, with biotremor production varying greatly between individuals. Biotremors were elicited by visual contact with another conspecific or heterospecific, and trials in which chameleons exhibited visual displays and aggressive behaviors were more likely to record biotremors. Three classes of biotremor were identified—hoots, mini-hoots, and rumbles, which differed significantly in fundamental frequency, duration, and relative intensity. Biotremor frequency decreased with increasing signal duration, and frequency modulation was evident, especially in hoots. Overall, the data show that C. calyptratus utilizes substrate-borne vibrational communication during conspecific and possibly heterospecific interactions.

 

Biotremors are vibrations, usually surface waves along the boundary of a medium, produced by an organism. While substrate-borne vibrations are utilized by different reptile species, true conspecific communication via biotremors has not yet been demonstrated in lizards. Recent research revealed that the veiled chameleon (Chamaeleo calyptratus) produces biotremors. The prerequisites for any communication system are the ability of an organism to produce and detect a signal. We tested C. calyptratus behavioral responses to vibrations by placing them on a dowel attached to a shaker, emitting vibrations of 25, 50, 150, 300, and 600 Hz and compared their locomotory velocity before and after the stimulus. Adult chameleons exhibited a freeze response to 50 and 150 Hz, while juveniles exhibited a similar response to frequencies between 50 and 300 Hz. In a second experiment, chameleons were induced to produce biotremors via experimenter contact. These biotremors ranged in mean fundamental frequency from 106.4 to 170.3 Hz and in duration from 0.06 to 0.29 s. Overall, two classes of biotremors were identified, “hoots” and “mini-hoots,” which differed significantly in mean relative signal intensity (−7.5 and −32.5 dB, respectively). Juvenile chameleons 2 months of age were able to produce biotremors, suggesting this behavior may serve a wide range of ecological functions throughout ontogeny. Overall, the data demonstrate that C. calyptratus can both produce and detect biotremors that could be used for intraspecific communication.

 

Abstract There is a growing recognition that responding to climate change necessitates urban adaptation. We sketch a transdisciplinary research effort, arguing that actionable research on urban adaptation needs to recognize the nature of cities as social networks embedded in physical space. Given the pace, scale and socioeconomic outcomes of urbanization in the Global South, the specificities and history of its cities must be central to the study of how well-known agglomeration effects can facilitate adaptation. The proposed effort calls for the co-creation of knowledge involving scientists and stakeholders, especially those historically excluded from the design and implementation of urban development policies. 

We propose a dedicated research effort on the determinants of settlement persistence in the ancient world, with the potential to significantly advance the scientific understanding of urban sustainability today. Settlements (cities, towns, villages) are locations with two key attributes: They frame human interactions and activities in space, and they are where people dwell or live. Sustainability, in this case, focuses on the capacity of structures and functions of a settlement system (geography, demography, institutions) to provide for continuity of safe habitation. The 7,000-y-old experience of urbanism, as revealed by archaeology and history, includes many instances of settlements and settlement systems enduring, adapting to, or generating environmental, institutional, and technological changes. The field of urban sustainability lacks a firm scientific foundation for understanding the long durée, relying instead on narratives of collapse informed by limited case studies. We argue for the development of a new interdisciplinary research effort to establish scientific understanding of settlement and settlement system persistence. Such an effort would build upon the many fields that study human settlements to develop new theories and databases from the extensive documentation of ancient and premodern urban systems. A scientific foundation will generate novel insights to advance the field of urban sustainability. 

A menudo se afirma que los asentamientos del sur de Mesoamérica representan un tipo de organización espacial distinto al de otros sistemas urbanos contemporáneos. Utilizando el marco analítico “escalado de asentamientos” investigamos las maneras específicas en las que los sistemas de asentamientos de Mesoamérica del Sur se asemejan, o no, a sistemas contemporáneos. Utilizamos la información registrada en sondeos de asentamientos Mayas y encontramos que la relación entre población y área difiere marcadamente de lo reportado para otros sistemas de asentamientos de carácter agrario. Notamos patrones más típicos cuando consideramos el epicentro de una zona arqueológica como el área de principal interacción social. Nuestros resultados implican que las poblaciones del sur de Mesoamérica poseían ritmos de interacción más lentos que la de otros sistemas urbanos contemporáneos. Las unidades familiares ubicaban sus residencias con el fin de equilibrar los costos de transporte ligados a la actividad agrícola y al desplazamiento a lugares centrales. El aumento de los rendimientos en actividades colectivas fueron realizadas a través de mezclas sociales de menor frecuencia. Concluimos que la principal diferencia entre el urbanismo Maya de baja densidad y otras experiencias urbanas contemporáneas tienen su origen en los patrones de movimiento asociados a las interacciónes sociales. 

Abstract We present three new analyses of existing data from past fieldwork at Teotihuacan. First, we confirm and refine the wealth-based housing typology of Millon's Teotihuacan Mapping Project (TMP). Second, we analyze the spatial configurations of excavated compounds, using network methods to identify the size and layout of individual dwellings within walled compounds. Third, we use those results to generate the first population estimate for the city based on measurements from the TMP map. We extrapolate the average sizes of dwellings from excavated compounds to the entire sample of mapped residences as depicted on the TMP map of the city. We generate a range of population estimates, of which we suggest that 100,000 persons is the most reasonable estimate for the Xolalpan-Metepec population of Teotihuacan. These analyses show that legacy data from fieldwork long past can be used to answer research questions that are relevant and important today. 

The Teotihuacan Mapping Project (TMP) provided vast quantities of invaluable data to our understanding of this famous ancient city. The ‘Documenting, Disseminating, and Archiving Data from the Teotihuacan Mapping Project’ aims to analyse, re-examine and ultimately coalesce TMP data for entry into The Digital Archaeological Record.