Resource use by howler monkeys (Alouatta palliata) in the rain forest of Los Tuxtlas,Veracruz, Mexico

The feeding preferences of howler monkeys at their northernmost distribution in the Neotropics are reported for an annual cycle. A remarkable selectivity for 27 species representing 15 families was observed. The Moraceae and Lauraceae plant families were the most important in the diet. The howlers spent an almost equal proportion of their feeding time eating leaves and fruit, and displayed a marked preference for young leaves and mature fruit. The consumption of different plant parts was markedly seasonal and the howlers’ ranging behavior was closely associated with the availability of young leaves and mature fruit. Their home range was unusually large (ca. 60 ha) for howlers and the food species exploited occur at very low densities (93%, ≤ 4 ind/ha). They chose food items richer in protein and energy. Alkaloid compounds, present in some of the leaves, play a secondary role in their dietary selectivity.     

Diet of the red howler monkey (Alouatta seniculus) in French Guiana

We report the feeding behavior and food preferences of a troop of red howler monkeys (Alouatta seniculus) over two annual cycles in primary tropical rain forest in French Guiana. The monkeys used 195 plant species from 47 families as food. Major food categories were young leaves (54%), mature fruits (21.5%), and flowers (12.6%). Other food categories included old leaves, immature fruits, termitarium soil, bark, and moss. The monkeys were less selective than other howler groups, since 19 plant species contributed 1% to their diet and accounted for only 35.7% of their total diet. The Sapotaceae was the most frequently eaten plant family and represented >10% of the total diet.     

Mandible/basihyal relationships in red howler monkeys (Alouatta seniculus): A craniometrical approach

The morphological relationships between the cranium and basihyal of red howler monkeys (Alouatta seniculus) were analyzed based on measurements of 36 cranial and 3 basihyal dimensions and observations of the female specimen in spirits. In this study, 115 crania from 111 red howler monkeys and 4 mantled howler monkeys (Alouatta palliata) were used. The analyses from the standpoints of the correlation coefficients, principal component analysis, discriminant function analysis, age changes and sex differences were performed and the following results were obtained: (1) The cranial measurements closely related to the basihyal measurements were mandibular length, occipital breadth, facial length, ramus height, cranial base length, bigonial breadth and pr-i length. (2) Age changes for the mandibular measurements in males of red howler monkeys were remarkable, and, in particular, the development of the gonion toward posterior and lateral directions were characteristic. (3) The largest sex differences were found in the mandibular measurements of red howler monkeys among the Anthropoidea of seven genera compared. (4) The existence of a “cline” in the cranial measurements of the red howler monkey was recognized. (5) The inter-species differences in the crania between the red howler monkey and mantled howler monkey are obvious, metrically and non-metrically. Based on the results mentioned above, the morphological relationships between the mandible and basihyal in the red howler monkey are discussed.     

Survey of the black howler monkey,<Emphasis Type="Italic">Alouatta pigra</Emphasis>, population at the Mayan site of Palenque,Chiapas, Mexico

A survey of the population of the black howler monkey (Alouatta pigra) present at the Mayan site of Palenque was conducted during 2000. A total of 911 man/hours, spread over 112 days were spent surveying the 600 ha area of pristine forest at the site for howler troops. We detected the presence of 136 individuals of which 131 were members of 20 troops, the rest were 3 solitary adult males and 2 adult males travelling as a pair. Ecological density was estimated at 23 individuals/km². Mean troop size was 7.0 individuals and it ranged from 2–12 individuals; 60% of the troops were multimale. All sighting of howler monkeys were in evergreen rain forest and 75% were in trees ≥20 m in height. The reported densities and mean troop size are higher than those reported for the species in Guatemala and in central Quintana Roo, Mexico. The vegetation of the forest contains tree species reported to be used by species ofAlouatta in the Moraceae, Sapotaceae, Leguminosae, and Lauraceae plant families. Protection of a large perimeter area (ca 1700 ha) around the archeological site by the Mexican government ensures the conservation of the forest and of the black howler monkey population present at the site.     

The functions of status in the mantled howler monkey,Alouatta palliata Gray: Intraspecific competition for group membership in a folivorous neotropical primate

In the dominance hierarchies of adult male and female mantled howler monkeys (Alouatta palliata Gray), high-ranking individuals are young adults; intermediate-ranking individuals, middle-aged adults; and low-ranking individuals, old adults. This relationship reverses the trend observed in most group-living animals and is previously unreported for this species. A limiting supply of palatable leaves may create intense intraspecific competition for group membership which, it is hypothesized, has resulted in this rare pattern of hierarchical relations. It is shown that individual-level selection is sufficient to explain the evolution of this apparently “altruistic” status system, though other mechanisms are assessed. The energetic constraints imposed by a folivorous diet appear to restrict the expression of aggression to “ritualized” forms. Two groups of monkeys in two different habitats were studied and the rates of appeasement and aggressive behavior were found to be higher in the more “stressful” forest. The latter group, however, displays significantly more behavioral patterns entailing low or intermediate energy expenditure.     

Feeding and general activity patterns of a howler monkey (Alouatta palliata) troop living in a forest fragment at Los Tuxtlas,Mexico

The feeding behavior and general activity patterns of a howler monkey troop living in a 3.6 ha forest fragment were studied at Los Tuxtlas, Mexico, for an annual cycle. Monthly samples of their feeding behavior indicated that they used 52 species of 24 plant families as sources of food. Of these, 67% were trees, which accounted for 96% of total feeding time recorded. Ten species of Moraceae, Cecropiaceae, Anacrdiaceae. and Sapotaceae contributed to 70% of the trees used and to almost 90% of feeding time. The number of plant species used per monthly record varied from 7 to 31 with an average of 19.9 species. Young leaves and ripe fruit were the principal items in the monthly diet of howlers and average percent of time spent consuming these plant parts was 46.7% and 34.8%, respectively. The use of tree species was found to be associated to their importance value and to their pattern of spatial dispersal in the study site. Availability of young leaves was fairly constant from month to month, but it presented a seasonal pattern, and there was a significantly lower number of tree species bearing ripe fruit through the year with brief pulses of production. The monthly activity pattern was found to be related to variations in the availability of young leaves and ripe fruit as well as to the values of the intermonthly overlap in plant species used. Resting and feeding presented a bimodal pattern of occurrence throughout the day that seemed to be related to variations in maximum ambient temperatures. Results are discussed in light of the small size and shape of the forest fragment inhabited by the howler troop. Am. J. Primatol. 48:167–183, 1999. © 1999 Wiley‐Liss, Inc.     

On the ecology and behavior ofCebus albifrons in eastern Colombia: I. Ecology

A-503 contact-hr study of a 35-member group ofCebus albifrons was conducted in eastern Colombia in 1977 and 1978. The group had a female: male socionomic sex ratio of 2.5:1 and used a home range of 110–120 ha which overlapped the home range of another group ofC. albifrons about 20–30 ha. The animals spent about 80% of their foraging time eating plant material and about 20% of their foraging time eating animal materials. A birth peak at the end of the dry season extending into the wet season was indicated by data available. Attempted predation was recorded by the mustelidEira barbara and the black-and-white hawk-eagleSpizastur melanoleucus. Some association was observed with the red howler monkeyAlouatta seniculus. The group at times spent more than half the day foraging and traveling on the ground, exhibiting a level of terrestriality not reported for other New World primates.     

Preliminary study of mother–offspring conflict in black and gold howler monkeys (<Emphasis Type="Italic">Alouatta caraya</Emphasis>)

Parent–offspring conflict has been scarcely studied in Neotropical primates. In this study, we explored mother–offspring conflict in a group of wild black and gold howler monkeys (Alouatta caraya) in northeastern Argentina. We used the all-occurrences technique to record behaviors, completing 712 h of observation. The results showed that all immature individuals between 2 and 23 months expressed conflict with regard to suckling or traveling with their mothers. Successful suckling attempts negatively correlated with the age of the immatures, occurring least frequently with the presence of newborns. In the juvenile period, the decline in successful attempts was a consequence of juveniles reducing suckling attempts and mother rejection.     

Movement and resource use by a group of <Emphasis Type="Italic">Alouatta pigra</Emphasis> in a forest fragment in Balancán,México

Uncommonly observed behaviors were systematically recorded in a troop (n = 9 individuals) of black howler monkeys (Alouatta pigra) inhabiting a small forest fragment (1.7 ha) in Leona Vicario, Balancán, Tabasco, Mexico. Between February 2002 and January 2003 (n = 499 h), we observed behaviors such as ground travel (85 occasions, total = 269 min/10.8% of total locomotion time), ground foraging (eight occasions, total = 50 min/0.84% of total feeding time) and drinking water pooled in tree holes (20 times, total = 93 min/0.31% of total activity time). Total time (412 min) for these non-resting behaviors (feeding and locomotion on the ground) is almost equivalent to time devoted to social activities (420 min). These behaviors indicate that howler monkeys may be responding to pressures imposed by the small size of the fragment by adopting diverse strategies to cover their basic nutritional needs in this environment. They accomplish this while exposing themselves to potential predation by coyotes (Canis latrans), as was observed once during the study. It is likely that these behaviors are occurring at an increasing rate among monkeys in fragmented landscapes.     

Calibration of LAI-2000 canopy analyser with leaf area index in a young eucalypt stand

Plant area index (PAI) measured with a LI-COR LAI-2000 plant canopy analyser (PCA) was calibrated with leaf area index (LAI) in a young stand of Eucalyptus grandis in the KwaZulu-Natal Midlands, South Africa. Destructive sampling and allometric equations were used to estimate LAI at 2 and 3 years after planting. Significant correlations (P<0.001) were found between LAI and PAI for each age with different equations being generated for the two ages (LAI=1.0594(PAI)−0.892 at 2 years of age, and LAI=1.0393(PAI) at 3 years of age). The equations differed from those reported in other eucalypt studies, as the PCA in this study over-predicted LAI at 2 years, and slightly under-predicted at 3 years, of age. It is argued that the stage of growth influenced this calibration, as the canopy and foliar structure may have been different in the young stands, affecting the basic assumptions for the PCA. A broad conversion from PCA derived PAI to LAI may not necessarily be valid for young, short rotation eucalypt plantations.     

Age-Dependent Variations of Volatile Emissions and Inhibitory Activity Toward <Emphasis Type="Italic">Botrytis cinerea</Emphasis> and <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> in Tomato Leaves Treated with Chitosan Oligosaccharide

We investigated variations in the level and composition of volatiles emitted by tomato leaves at different ages. Our focus also included their antifungal properties and responses to chitosan oligosaccharide. Based on leaf position, the release of volatiles decreased over time. Young leaves produced high levels of C6-aldehyde, which is mainly composed of hexenal, while the volatiles emitted by more mature leaves largely comprised terpenes, particularly β-phellandrene and caryophyllane. In young upper leaves, the main components (up to 86% of the total) were hexenal, β-phellandrene, and caryophyllane. Their levels decreased steadily over time, from 386.3 μg g⁻¹ fresh weight (FW) in young leaves to 113.2 μg g⁻¹ FW in old tissues. Volatiles emitted from young leaves exhibited the best antifungal activity against spore germination and hyphal growth by Botrytis cinerea and Fusarium oxysporum. Leaves became more susceptible to oligosaccharide treatment with increasing age. When young tissues were exposed to chitosan, we found declines in both the quantity of volatiles and their ability to inhibit fungal growth. Compared with the control, the amount of volatiles from young tissues was 88.4% lower after such treatment. In contrast, contents of volatiles from old and adult leaves were dramatically increased by chitosan oligosaccharide. Likewise, their inhibitory effect was significantly enhanced. Therefore, our results suggest that these volatiles are responsible for antifungal activity and may play a role in age-related resistance by tomato.     

Maternal Watchfulness in Black Howler Monkeys (Alouatta pigra)

In many vertebrates, parents protect their young by detecting predators and aggressive conspecifics before they attack. But parental investment in protection is a limited resource, whose allocation to offspring should reflect optimization strategies. Thus, we tested if maternal investment in vigilance varied with the risk faced by young black howler monkeys (Alouatta pigra). Twelve females in six groups were compared, including those with and without young and those with immatures of differing ages. The greatest increase in vigilance was seen when immatures were conspicuous, and to a lesser extent, among mothers of dependent young (neonates and infants). These findings support the idea that parents adjust their behavior to both chronic and episodic risk faced by young. We explore the possible role of predation and infanticide in shaping the vigilance of mothers.     

Reproductive patterns in mantled howler monkeys: Estrus,mate choice and copulation

The present study was undertaken to evaluate non-random mating patterns in two groups of mantled howler monkeys in two tropical dry forest habitats. Sexual dimorphism, female estrus stage, male dominance rank, sexual solicitations and copulations were assessed. Males are significantly larger than females, but female weight varies more than male weight. The length of female estrus cycles is comparable in both habitats, but females in the more strongly seasonal habitat demonstrate greater estrus synchrony relative to their numbers. Males solicit potential mates more frequently than females, a pattern explained by the relatively high rate of sexual solicitation by high-ranking males. Females in “peak” estrus solicit “alpha” males, while females in other stages of estrus solicit males equally by rank. Intersexual aggression occurs rarely, and “forced copulations” are attempted but, apparently, are unsuccessful. Sexual solicitations by “alpha” males and “peak” estrus females are most likely to lead to copulation, and “alpha” males are more likely to copulate than “gamma” males. In general, latencies from first solicitation to copulation are expensive in time, especially for high-ranking males. Estimated annual reproduction success favors high-ranking males, and results indicate that male and female mating behavior is mutually coordinated and controlled.     

Mother-Young Feeding Synchrony and Early Food Selection Differences in Eulemur fulvus

I tested the hypothesis that mother-young cofeeding correlates with a systematic similar food selection in wild Mayotte brown lemurs (Eulemur fulvus). I simultaneously recorded the feeding behavior of 4 maternal dyad members, from infant birth to weaning, and 10–12 mo of juvenile age, during 10-min focal periods, each separated by 5-min intervals over 10 mo. I recorded the solid food items selected for each feeding behavior at the level of specific plant part, along with the distance between the 2 individuals. I considered feeding behaviors simultaneous (between the young lemurs and their mothers) when the young began to eat a food item while the mother was already eating, regardless of the separation distance. During their first year, most of the feeding events of the young brown lemurs were initiated by their mothers. However, infants also selected different food items from those chosen by their mothers in almost one-third of cases, and the food selection dissimilarity was not attributable to an increase in the distance of separation. For juveniles, dissimilar food selection was significantly lower and linked to an increase in mother-juvenile separation distance. Thus, the substantial proportion of dissimilarity in solid foods selected by the infant during the synchronized feeding behaviors strongly suggests that social influences were not food-specific and might instead drive the acquisition of group feeding activity rhythm rather than food selection habits.     

Host age and host selection byTrichogramma nubilale

Selection byTrichogramma nubilale (Ertle & Davis) for different aged egg masses ofOstrinia nubilalis (Hübner) was examined by separating components of parasitism. FemaleT. nubilale were exposed to egg masses of 2 different ages (freshly laid egg masses versus 1, 2, 3 or 4 day old egg masses), and the age of the initial egg mass inspected, number and percent of eggs and egg masses parasitized, and the emergence rate of pharate parasitoids was recorded. When there was a large difference in age between young and old egg masses, ♀♀ inspected initially more young egg masses (>2 days difference), parasitized a greater percent of young egg masses (>2 days difference), and parasitized more eggs/parasitized egg mass in young egg masses (>3 days difference) than old egg masses. Females did not discriminate between host age when hosts were similar in age. Successful emergence of parasitoids was greater from younger eggs than older eggs, although emergence was better from one-day-old eggs than from fresh eggs. These results imply that when the hosts were sufficiently different in age, ♀♀ were attracted to younger egg masses more than older egg masses, and they tended to remain ovipositing for longer periods of time on younger egg masses than older egg masses. Moreover, ♀♀ appeared to prefer to oviposit in hosts in which their young are more likely to complete development.      

<Emphasis Type="Italic">Aloe vera</Emphasis> transformation: the role of Amberlite XAD-4 resin and antioxidants during selection and regeneration

A system for genetic transformation and subsequent plant regeneration via indirect organogenesis from callus was developed for Aloe vera. Young seedlings served as primary explants. Callus cultures were established on Murashige and Skoog (1962) medium supplemented with 3 mg l⁻¹ benzylaminopurine and 2 mg l⁻¹ indole acetic acid. A protocol was developed to switch from the differentiated stage, using in vitro shoots or young regenerated plants, back to the de-differentiated stage of the callus and vice versa. Long-term maintenance of this callus paved the way for genetic manipulation of Aloe vera. Calluses were bombarded with a plasmid containing uidA and hpt genes, both under the control of the 35S promoter. Dithiothreitol and gibberellic acid were found to play a major role in reducing tissue necrosis following bombardment. Transformed shoots were regenerated under stepwise selection in hygromycin-containing liquid medium supplemented with different antioxidants. Amberlite XAD-4 resin was embedded into alginate beads and added to the selection medium. Amberlite was best for adsorbing different phenolic compounds and blocking explant necrosis. Shoot initiation occurred after transfer of the transformed cells to Murashige and Skoog medium supplemented with 2.0 mg l⁻¹ thidiazuron and 0.1 mg l⁻¹ indole butyric acid. Murashige and Skoog medium supplemented with 1 mg l⁻¹ zeatin riboside promoted shoot elongation. Rooting and plant development were obtained on Murashige and Skoog basal medium supplemented with 15 mg l⁻¹ hygromycin lacking growth regulators. The transgenic nature of the regenerated plants was verified by histochemical GUS assay and Southern blot hybridization.     

Host Selection by the Herbivorous Mite Polyphagotarsonemus latus (Acari: Tarsonemidae)

This study examined the host-selection ability of the broad mite Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae). To make long-distance-shifts from one host plant patch to another, broad mites largely depend on phoretic association with whiteflies. However, the host plants of whiteflies and broad mites are not necessarily the same. We determined the host-preference and acceptance of free-moving and phoretic broad mites using two behavioral bioassays. We used a choice test to monitor host selection by free-moving mites. In the case of phoretic mites, we compared their rate of detachment from the phoretic vector Bemisia tabaci placed on leaves taken from various host plants. The suitability of the plant was further determined by monitoring mite’s fecundity and its offspring development. We compared the mites’ responses to young and old cucumber (Cucumis sativus cv. ‘Kfir’) leaves (3rd and 8–9th leaf from the apex, respectively), and two tomato (Solanum lycopersicum cvs. ‘M82’ and ‘Moneymaker’). Free-moving mites of all stages and both sexes preferred young cucumber leaves to old cucumber leaves and preferred young cucumber rather than young tomato leaves, demonstrating for the first time that broad mites are able to choose their host actively. As for phoretic mated females, although eventually most of the mites abandoned the phoretic vector, the rate of detachment from the whitefly vector was host dependent and correlated with the mites’ fitness on the particular host. In general, host preference of phoretic female mites resembled that of the free-moving female. Cues used by mites for host selection remain to be explored.     

Anthropogenic edges impact howler monkey (Alouatta palliata) feeding behaviour in a Costa Rican rainforest

Anthropogenic forest fragmentation impacts many aspects of animal behaviour, including feeding ecology. With forests increasingly fragmented in tropical regions due to human development, the proportion of forest edge (≤?100 m from clear-cut regions) is higher relative to forest interior. Forest edges differ in vegetation from interior, making it important to better understand how anthropogenic edges impact the feeding behaviour of primates such as mantled howler monkeys (Alouatta palliata). We predicted that howler monkeys would feed on higher-quality plant resources, from a larger number of tree families, and from larger trees in forest interior compared to anthropogenic forest edge. We surveyed howler monkey feeding behaviour across forest zones in a fragmented rainforest in Costa Rica, La Suerte Biological Research Station. We observed individual monkeys for 30-minute periods, collecting data on their feeding behaviour and tree use at 2-minute intervals. We measured feeding trees and recorded the plant parts and taxonomy of resources consumed. Monkeys consumed more leaves and fewer stems and fed from a smaller number of tree families in the forest interior, while they consumed fewer leaves and more stems and fed from a larger number of tree families in the forest edge. Monkeys also fed from larger, taller trees in the forest interior than the edge. The differences in howler monkey feeding behaviour between forest zones attest to the impact of human disturbance on howler monkey feeding ecology.

     

Successional loss of two key food tree species best explains decline in group size of Panamanian howler monkeys (Alouatta palliata)

Negative impacts of discrete, short‐term disturbances to wildlife populations are well‐documented. The consequences of more gradual environmental change are less apparent and harder to study because they play out over longer periods and are often indirect in their action. Yet, they can drive the decline of wildlife populations even in seemingly pristine and currently well‐protected habitats. One such environmental change is a successional shift in a community's species composition as it regenerates from disturbance caused by past human land use. Early and middle successional tree species often provide key foods to folivores and frugivores, but the abundance of these resources drops as the forest matures, with adverse repercussions for these consumers. Our 44‐year record (1974–2018) of howler monkey (Alouatta palliata) group sizes and demographic composition from Barro Colorado Island, Panama, a protected reserve, documents an example of this phenomenon. After 70 years of relative stability, the mean size of howler monkey groups exhibited a marked decline, beginning in 2003. This downward trajectory in group size has continued through the most recent census in 2018. The composition of howler groups also changed significantly during the study period, with the patterns of decline differing among age/sex classes. There is no evidence that these changes were caused by increased rates of emigration, group fission, predation, parasitism, or disease. Rather, they are best explained by an island‐wide, succession‐driven decline in the densities of two species of free‐standing fig trees, Ficus yoponensis and F. insipida, which together were providing ~36% of BCI howlers’ annual diet. Abstract in Spanish is available with online material.