Browsing by Author "Soto-Gamboa, Mauricio"

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    Allosuckling allows growing offspring to compensate for insufficient maternal milk in farmed guanacos (Lama guanicoe)
    (2010) Zapata, Beatriz; Correa, Loreto; Soto-Gamboa, Mauricio; Latorre, Etel; Gonzalez, Benito A.; Ebensperger, Luis A.
    While allonursing, the provision of milk to non-offspring by females, involves a potential cost to their own offspring, allosuckling, the suckling from females other than their own mother may allow offspring to compensate for previous deficiencies in maternal milk. We tested this hypothesis in farmed guanacos. Under the compensation hypothesis we predicted that mothers of calves exhibiting allosuckling should be in poorer physical condition and should exhibit relatively low acceptance rates to filial sucking attempts compared to mothers whose calf did not allosuckle. We also predicted that calves exhibiting frequent allosuckling should show similar or greater rates of gain in body weight. but similar total (or final) weight in the long term than calves that nursed from their mothers exclusively. We examined the potential effects of sex and order of birth dates of calves on allosuckling, and the effect of female Success during agonistic encounters with other females on allonursing. Two stable groups of 15 and 14 mother-offspring pairs of farmed guanacos were studied from birth to approximately 3 months of age. Allosuckling events comprised 5.7% of all suckling events. Allonursing was performed by 52% of dams and 62% of calves exhibited allosuckling. We found similar gain rates in body weight and total weight at 60 days of age between allosuckling calves and filial sucking calves, irrespective of whether their mothers allonursed or not (P > 0.1). Body weight of mothers whose calf allosuckled was significantly lower than that of mothers whose calves nursed from them exclusively (P = 0.02). In addition, the percentage of acceptance of filial suckling bouts was significantly lower for allosuckling calves (P = 0.004). There was no correlation between the frequency of allonursing and the success of dams during agonistic encounters (P > 0.22). Our findings are consistent with the hypothesis that guanaco calves used allosucking to compensate for previous deficiencies in maternal milk. (C) 2009 Elsevier B.V. All rights reserved.
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    Automatic Recognition of Black-Necked Swan (Cygnus melancoryphus) from Drone Imagery
    (2023) Jimenez-Torres, Marina; Silva, Carmen P. P.; Riquelme, Carlos; Estay, Sergio A. A.; Soto-Gamboa, Mauricio
    Ecological monitoring programs are fundamental to following natural-system populational trends. Drones are a new key to animal monitoring, presenting different benefits but two basic re-strictions First, the increase of information requires a high capacity of storage and, second, time invested in data analysis. We present a protocol to develop an automatic object recognizer to minimize analysis time and optimize data storage. We conducted this study at the Cruces River, Valdivia, Chile, using a Phantom 3 Advanced drone with an HD-standard camera. We used a Black-necked swan (Cygnus melancoryphus) as a model because it is abundant and has a contrasting color compared to the environment, making it easy detection. The drone flew 100 m from water surface (correcting AGL in relation to pilot landing altitude) obtaining georeferenced images with 75% overlap and developing approximately 0.69 km(2) of orthomosaics images. We estimated the swans' spectral signature to build the recognizer and adjusted nine criteria for object-oriented classification. We obtained 140 orthophotos classified into three brightness categories. We found that the Precision, Sensitivity, Specificity, and Accuracy indicator were higher than 0.93 and a calibration curve with R2= 0.991 for images without brightness. The recognizer prediction decreases with brightness but is corrected using ND8-16 filter lens. We discuss the importance of this recognizer to data analysis optimization and the advantage of using this recognition protocol for any object in ecological studies.
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    Fecal cortisol levels predict breeding but not survival of females in the short-lived rodent, Octodon degus
    (2013) Ebensperger, Luis A.; Tapia, Diego; Ramirez-Estrada, Juan; Leon, Cecilia; Soto-Gamboa, Mauricio; Hayes, Loren D.
    The cort-adaptation hypothesis indicates that an association between glucocorticoid (cort) levels and fitness may vary with the extent to which reproduction or breeding effort is a major determinant of cort levels. Support for a context dependent association between cort and fitness comes mostly from relatively long-lived, bird species. We tested the hypothesis that there are gender and context (life-history) specific cort-fitness relationships in degus, a short-lived and generally semelparous social rodent. In particular, we used demographical records on a natural population to estimate adult survival through seasons and years and linked that to records of baseline cort (based on fecal cortisol metabolites). We found no evidence for a direct relationship between baseline cort and adult survival across seasons, and this lack of association was recorded irrespective of sex and life history stage. Yet, cort levels during early lactation predicted the probability that females produce a second litter during the same breeding season, supporting a connection between baseline cort levels and breeding effort. Overall, the differential effects of cort on survival and breeding supported that the extent of cort-fitness relationships depends on the fitness component examined. (C) 2013 Published by Elsevier Inc.
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    Natural history of the relict marsupial Monito del Monte at the most extreme altitudinal and latitudinal location
    (2021) Mejias, Carlos; Castro-Pastene, Carlos A.; Carrasco, Hector; Quintero-Galvis, Julian F.; Soto-Gamboa, Mauricio; Bozinovic, Francisco; Nespolo, Roberto F.
    Until a few years ago, the "monito del monte" (Dromiciops gliroides) was considered the sole surviving species of Microbiotheria, the sister group of Australidelphia (Australian marsupials). However, the recent identification of a new species relegated to the northern range (Dromiciops bozinovici) and newly discovered populations of Dromiciops beyond the known limits for the geographic range demands for new studies in extreme locations. In this report, we describe the northernmost population of D. bozinovici at a high Andean location (Reserva Nacional Altos de Lircay [RNAL], which represents a record of Dromiciops distribution both in latitude [35 degrees S] and in altitude [1696 m a.s.l.]). We live-trapped individuals, performed behavioral observations, and extracted mtDNA (Cytb) for analyzing phylogenetic affinities. Together with confirming the phylogenetic position of RNAL within the D. bozinovici clade, interesting aspects of this isolated population arose, such as the sympatry with a didelphid marsupial (Thylamys elegans), and phylogenetic closeness with populations 300 km southward coastal. Our trapping effort yielded approximately 9.3 individuals/ha, which is relatively high compared with other small mammal populations, but typical for Dromiciops. Using in situ thermographic imaging during a night transect, we detected free-ranging animals running vertically at similar to 3.6 km/h through the logs of mature trees (Nothofagus pumilio), which is fast compared with other small runners (e.g., cursorial rodents), and also compared with Dromiciops from other locations. We compared the critical time to escape, of RNAL individuals which resulted significantly higher than Dromiciops from Nahuelbuta and Valdivia, suggesting that animals from RNAL are more tolerant to human presence than other populations, which is probably due to the high level of isolation of this population. According to the IUCN the northernmost distribution of Dromiciops reaches Cauquenes, thus this report extends the distribution in 120 km to the North East. Interesting aspects, such as hibernation at freezing temperatures and the existence of a viable D. bozinovici population northward of RNAL, warrant further research on this interesting location.
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    One for all and all for one: phenotype assortment and reproductive success in masculinized females
    (2021) Correa, Loreto A.; Leon, Cecilia; Ramirez-Estrada, Juan; Ly-Prieto, Alvaro; Abades, Sebastian; Hayes, Loren D.; Soto-Gamboa, Mauricio; Ebensperger, Luis A.
    Homophily by morphological and behavioral traits has been described in several species of vertebrates, but its functional consequences remain poorly studied. Homophily by plurally breeding females may improve direct fitness by enhancing reproductive success. Female mammals may exhibit phenotypical masculinization due to exposure to androgens during early development, a condition that is associated with maternal performance during subsequent breeding. Our goal was to assess whether female composition (in terms of masculinization) of plurally breeding groups influences female fitness in a natural population of degus (Octodon degus). We assessed if plurally breeding female degus assort themselves by anogenital distance (AGD), an accurate measure of masculinization level. We also quantified if homophily by AGD phenotype affects female reproductive success and the reproductive output of the group. Plurally breeding groups typically included similarly masculinized (i.e., long AGD) females or similarly feminized (short AGD) females, indicating a strong degree of homophily. Females weaned more offspring in plurally breeding groups with more masculinized females. Additionally, standardized variance in the number of offspring weaned decreased in plurally breeding groups with mostly masculinized females, indicating greater reproductive equality in these groups. We conclude that female degus organize into homophilic social groups of similar AGD, and that social groups of masculinized females exhibit a higher reproductive success.
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    Social environment and anogenital distance length phenotype interact to explain testosterone levels in a communally rearing rodent: Part 1: The male side
    (2024) Correa, Loreto A.; Aspillaga-Cid, Antonia; Bauer, Carolyn M.; Silva-Alvarez, Danna; Leon, Cecilia; Ramirez-Estrada, Juan; Soto-Gamboa, Mauricio; Hayes, Loren D.; Ebensperger, Luis A.
    In vertebrates, male testosterone levels vary across the year being generally higher during the mating season relative to the offspring rearing season. However, male testosterone levels may also be associated with male anogenital distance (AGD) length (a proxy of prenatal androgen exposition), and influenced by the social group environment. In social species, it has been proposed that high levels of testosterone could be incompatible with the development of an amicable social environment. Thus, in these species, it is predicted that males have relatively low levels of testosterone. Our goal was to examine the potential association between male serum testosterone levels, season, male AGD length, and the social environment in the rodent Octodon degus under natural conditions. We quantified male serum testosterone levels during the mating and offspring rearing seasons, and we determined the number of females and males in each social group, as well as the composition of groups, in terms of the AGD length of the female and male group mates, from 2009 to 2019. Our results revealed that male testosterone levels covary with season, being highest during the offspring rearing season. Additionally, male testosterone levels vary with male AGD length, and female and male social group environments. More importantly, male degus exhibit low levels of testosterone that are indistinguishable from female levels during offspring rearing season. Similar to other highly social mammals, where males and females live together yearround, male amicable behavior could be the best male mating strategy, thus leading to a reduction in circulating testosterone levels.
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    Social environment and anogenital distance length phenotype interact to explain testosterone levels in a communally rearing rodent: Part 2: The female side
    (2024) Correa, Loreto A.; Aspillaga-Cid, Antonia; Leon, Cecilia; Bauer, Carolyn M.; Ramirez-Estrada, Juan; Hayes, Loren D.; Soto-Gamboa, Mauricio; Ebensperger, Luis A.
    Testosterone is known as a "male" hormone; however, females also synthetize testosterone, which influences female sexual and aggressive behavior. In female vertebrates, as in males, testosterone levels can vary seasonally. However, female testosterone levels may also be related with female anogenital distance (AGD) length phenotype (a proxy of prenatal androgen exposure), and the social group environment. We used data from a long -term rodent study (2009-2019) in a natural population of degus (Octodon degus) to examine the potential associations between female serum testosterone levels, season, female AGD phenotype, and social group composition. We quantified female serum testosterone levels during the mating and offspring rearing seasons, and we determined the number of females and males in social groups, as well the composition of groups, in terms of the AGD of the female and male group mates. Our results indicate that female testosterone levels vary with season, being highest during the offspring rearing season. Additionally, female testosterone levels were associated with the number of male group-members and the AGD of male group-members but were not associated with female social environment and focal female AGD phenotype. Together, our results suggest that female testosterone levels are sensitive to intersexual interactions. Our results also reveal that female and male testosterone levels do not differ between the sexes, a finding previously reported only in rock hyraxes. We discuss how the complex social system of degus could be driving this physiological similarity between the sexes.
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    The role of gastrolites on feeding behavior and digestive efficiency in the Rufous-collared Sparrow
    (2000) López-Calleja, M. Victoria; Soto-Gamboa, Mauricio; Rezende Landaeta, Enrico
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