Nest Excavation Research Articles

Nest excavators’ learning walks in the Australian desert ant Melophorus bagoti

The Australian red honey ant, Melophorus bagoti, stands out as the most thermophilic ant in Australia, engaging in all outdoor activities during the hottest periods of the day during summer months. This species of desert ants often navigates by means of path integration and learning landmark cues around the nest. In our study, we observed the outdoor activities of M. bagoti workers engaged in nest excavation, the maintenance of the nest structure, primarily by taking excess sand out of the nest. Before undertaking nest excavation, the ants conducted a single exploratory walk. Following their initial learning expedition, these ants then engaged in nest excavation activities. Consistent with previous findings on pre-foraging learning walks, after just one learning walk, the desert ants in our study demonstrated the ability to return home from locations 2 m away from the nest, although not from locations 4 m away. These findings indicate that even for activities like dumping excavated sand within a range of 5–10 cm outside the nest, these ants learn and utilize the visual landmark panorama around the nest.

First description of the breeding biology and behaviour of the near threatened northern sooty woodpecker <i>Mulleripicus funebris</i> (Valenciennes 1826) (Piciformes: Picidae) in Luzon Island, Philippines

Although generally regarded as keystone species within forest communities, woodpeckers (Picidae) remain understudied in the Philippines. We describe for the first time the breeding biology and behaviour of the IUCN Near Threatened northern sooty woodpecker Mulleripicus funebris based on observations from a single active nest found in a standing dead Parkia timoriana tree at the Subic Watershed Forest Reserve, Zambales, Luzon, Philippines. The nest was observed from late February to May 2022 for a total of 63.7 hours. The cavity was 16.4 m from the ground and had opening dimensions (L x W) of 9.0 x 8.0 cm and a depth of 37.0 cm. Breeding of M. funebris lasted ≈76-83 days from nest excavation (≈27 days) to fledging. The brood size was two. Both parents were involved in nest building and chick-rearing activities. The male M. funebris contributed more hours during nest building and diurnal incubation whereas the female dominated feeding of nestlings and nest sanitation during the time of fledging. We recommend the retention of standing dead trees as nesting sites for woodpeckers and already existing holes for other cavity-nesting fauna.

First report of the egg fertility of the hawksbill turtle (Eretmochelys imbricata) (Testudines: Cheloniidae) in Melaka, Malaysia

The unhatched eggs of the hawksbill turtle (Eretmochelys imbricata) are often found in the hatchery in Melaka, Malaysia, raising concerns if the eggs remain unfertilized. Examining unhatched eggs during post-emergence nest excavation could lead to eggs being mistakenly identified as unfertilized eggs due to the difficulty in differentiating between unfertilized eggs and early embryonic mortality. It is essential to determine the egg fertility of hawksbill turtles in Melaka before concluding that hatching failure is due to infertility. Egg fertility was determined using the white spot method conducted at the beginning of egg incubation on 50 clutches. Mean egg fertility was 85.9%, but the mean hatching success was significantly lower at 57.6% (mean emergence success was 56.8%). The results showed that egg fertility did not reflect hatching success and infertility was unlikely the cause of hatching failure. The huge number of undeveloped eggs may have been due to early embryonic death that went undetected at the end of incubation.

Long‐term habitat degradation affects nest site selection behaviour by a freshwater turtle (Chelodina oblonga) in Western Australia

Abstract Freshwater turtles are one of the most endangered vertebrate groups with >60% of species threatened globally. Terrestrial nesting habitat degradation is a major threat to freshwater turtles, but the characteristics of nesting habitat remain poorly understood. This study investigated the nest site selection of the southwestern snake‐necked turtle (Chelodina oblonga) to improve the conservation prospects for this species in an urbanized wetland area. In total, 235 depredated and 86 non‐depredated nest sites and 320 non‐nest locations were surveyed at Bibra Lake, Western Australia, during the Austral spring–summer, 2018–2023. A suite of environmental variables was measured at nest sites and non‐nest locations. Analysis of similarities was used to determine whether nest sites and non‐nest locations differed in their environmental characteristics. Generalized linear mixed models were used to identify environmental variables that best explained the nesting preferences. The environmental characteristics of nest sites differed from those of non‐nest locations, with turtles nesting mainly in remnant natural habitat with greater canopy cover. Turtles generally avoided nesting in modified environments such as lawns and impervious surfaces. Factors influencing nest site selection are probably associated with the conditions necessary for regulating incubation temperatures and ease of nest excavation. This study suggests that modification of terrestrial vegetation around wetlands is adversely affecting freshwater turtle recruitment by removing or altering preferred nesting habitat. Protection and restoration of natural habitats fringing urban wetlands is important for the conservation of remnant freshwater turtle populations, and local partnership projects can help to achieve this.

The role of Magellanic penguins (Spheniscus magellanicus) on landscape dynamics and lithic taphonomy in La Pastosa Islet, North Patagonia, Argentina

This study presents the results of a systematic survey of La Pastosa Islet, located 700 m off the west coast of Río Negro, Argentina. This small islet has the particularity of hosting the northernmost colony of Magellanic penguins ( Spheniscus magellanicus) to date and contains evidence of its use by hunter-gatherer groups during the late Holocene. This growing colony started around 2002 and has had a significant impact on the subsurface archeological record of the islet by increasing erosion and exposing buried materials through nest excavation, particularly lithic artifacts. The spatial analysis of the distribution of artifact and penguin burrows indicates that the actions of the latter generated a “snapshot” of the subsurface distribution of the lithic record. The observed distribution suggested higher discard rates at the center of the islet. Furthermore, this study shows the synergy between both types of records in the formation dynamics of the lithic landscape and the agency of penguins as active landscape engineers. Finally, the obtained results have important implications for the management of the protected sector of the recently established Islote Lobos National Park, within which the study area is located.

Two new Hoplitis species of the subgenus Hoplitis Klug, 1807 (Hymenoptera, Megachilidae) and the nesting biology of H. astragali sp. nov. in Dagestan

Hoplitis astragalisp. nov., a member of the H. monstrabilis species group, and H. dagestanicasp. nov., a member of the H. adunca species group, are described. The former species is known from Dagestan in Russia, Azerbaijan, and Turkmenistan, the latter only from Dagestan. Nests of H. astragali are described. Females of this species excavated burrows in a vertical clay cliff, but sometimes chose a horizontal surface for nest excavation, particularly at the entrance of old burrows of Xylocopa olivieri (Apidae). The nest burrows of H. astragali were either sub-vertical or sub-horizontal. The nests were composed of one to three brood cells, an empty vestibule in front of the outermost cell, and a closing plug at the nest entrance made of moistened mud. The inner surface of the cells was covered with a thin wall composed of compact soil, most probably built by the female bee after cell excavation. The pollen loaf was very liquid and had a spherical shape. The egg was deposited on its top. The cocoon consisted of a single thin layer, which uniformly covered the whole inner surface of the cell. There was one generation per year. The prepupae hibernated. Sapyga caucasica (Sapygidae) was recorded in the nests as a kleptoparasite. Both females and males of H. astragali exclusively visited flowers of two species of the genus Astragalus (Fabaceae).

TManual: Assistant for manually measuring length development in structures built by animals.

Structures built by animals are extended phenotypes, and animal behavior can be better understood by recording the temporal development of structure construction. For most subterranean and wood-boring animals, these structures consist of gallery systems, such as burrows made by mice, tunnel foraging by termites, and nest excavation in ants. Measurement of the length development of such structures is often performed manually. However, it is time-consuming and cognitively costly to track length development in nested branching structures, hindering the quantitative determination of temporal development. Here, I introduce TManual, which aids the manual measurement of structure length development using a number of images. TManual provides a user interface to draw gallery structures and take over all other processes handling input datasets (e.g., zero-adjustment, scaling the units, measuring the length, assigning gallery identities, and extracting network structures). Thus, users can focus on the measuring process without interruptions. As examples, I provide the results of the analysis of a dataset of tunnel construction by three termite species after successfully processing 1125 images in ~3 h. The output datasets clearly visualized the interspecific variation in tunneling speed and branching structures. Furthermore, I applied TManual to a complex gallery system by another termite species and extracted network structures. Measuring the lengths of objects from images is an essential task in biological observation. TManual helps users handle many images in a realistic time scale, enabling a comparative analysis across a wide array of species. TManual does not require programming skills and outputs a tidy data frame in CSV format. Therefore, it is suitable for any user who wants to perform image analysis for length measurements.

Wing and tail feather damage in Western Common Kingfishers Alcedo atthis ispida in relation to moult

ABSTRACT Feathers have to be moulted to repair sustained damage. Our objective is to understand the relationship between the frequency of feather damage, feather sturdiness and moult sequence. Damage was recorded in five flight feather tracts for over 2000 Common Kingfishers Alcedo atthis ispida captured during a population study in northwestern Germany. We found that, of the feather tracts studied before the first moult, the tail feathers sustained most wear and damage, especially the more sturdily built outermost ones. Nevertheless, the probability of moulting a rectrix decreased from the central pair to the outside, while the damage risk increased. The sturdy distal primaries and the more lightly built innermost secondaries were the remiges with the highest frequency of damage, but not the most severe damage, while a row of midwing secondaries and primaries had the lowest damage risk. Where remiges had been retained when moult was suspended at the beginning of winter, about 75% of unmoulted feathers belonged to this low-risk group. The distal alula feather and the outermost primary covert had damage rates comparable to the low-risk row of remiges. Feather damage in the wings does not accumulate evenly over time, but increased markedly from March to April, coinciding with courtship and nest excavation, especially in females. Ultraviolet light seems to be an important factor for the observed feather deterioration, but is not the only one. The Kingfisher’s unusual moult sequence of remiges and primary coverts matches the distribution pattern of feather damage, but the sequence of the first tail-feather moult does not. Very few previous studies have investigated the relationship between patterns of feather damage and moult sequence. We hope this work encourages more investigation of this subject.

Agitated ants: regulation and self-organization of incipient nest excavation via collisional cues.

Ants are millimetres in scale yet collectively create metre-scale nests in diverse substrates. To discover principles by which ant collectives self-organize to excavate crowded, narrow tunnels, we studied incipient excavation in small groups of fire ants in quasi-two-dimensional arenas. Excavation rates displayed three stages: initially excavation occurred at a constant rate, followed by a rapid decay, and finally a slower decay scaling in time as t-1/2. We used a cellular automata model to understand such scaling and motivate how rate modulation emerges without global control. In the model, ants estimated their collision frequency with other ants, but otherwise did not communicate. To capture early excavation rates, we introduced the concept of 'agitation'-a tendency of individuals to avoid rest if collisions are frequent. The model reproduced the observed multi-stage excavation dynamics; analysis revealed how parameters affected features of multi-stage progression. Moreover, a scaling argument without ant-ant interactions captures tunnel growth power-law at long times. Our study demonstrates how individual ants may use local collisional cues to achieve functional global self-organization. Such contact-based decisions could be leveraged by other living and non-living collectives to perform tasks in confined and crowded environments.

Corozalito: a nascent arribada nesting beach in Costa Rica.

Costa Rica hosts two renowned olive ridley (Lepidochelys olivacea) arribada beaches: Nancite and Ostional. In addition, the country hosts a third nascent arribada beach in Corozalito. We documented the frequency of arribada events in Corozalito (9°50′55.40″ N; 85°22′ 47.67″ W) from 2008 to 2021 and the abundance of egg-laying females during 12 arribadas. Moreover, we report on tag recaptures at Corozalito that were initially deployed at other nesting beaches in Costa Rica. Finally, we estimated incubation temperature, and performed quadrat and nest excavations to estimate hatching rates. We registered 29 arribadas at Corozalito since 2008, all between August and January. We estimated more than 150,000 olive ridleys nested during 12 arribadas from 2019 to 2021. Mean hatching success was 65% in quadrats and 59% for in situ marked nests. The mean incubation temperature was 32.3 °C. We found turtles tagged at other locations on the Pacific coast of Costa Rica nesting at Corozalito, providing evidence of philopatric plasticity. We suggest nascent arribada rookeries form rapidly via recruitment from regional turtle aggregations. Our findings show that hatching success is far higher at Corozalito than Ostional or Nancite. Continued monitoring of nesting dynamics at this site may shed light upon the mechanisms that rule how arribada beaches are born and evolve. Corozalito offers a unique opportunity to study and understand the arribada phenomenon and warrants official protection under official National Wildlife Refuge status.

Presumptive nest excavation by a Banded Racer (Platyceps plinii)

Presumptive nest excavation by a Banded Racer (Platyceps plinii)

Finding of a two-headed green turtle embryo during nest monitoring in Baa Atoll, Maldives.

Green sea turtles are one of the two species of marine turtles known to nest in the Maldives. The prevalent time of nesting seems to be inconsistent throughout the island nation. In this study, sea turtle nesting activity was monitored on the island of Coco Palm Dhuni Kolhu in Baa Atoll over a period of 12 months. A total of 13 nests were confirmed with a median hatching success rate of 89.58% as ascertained by nest excavation. In one of the nests, a severely deformed hatchling with polycephaly, an opening in the neck area and a lordotic spine was found, and we investigated in detail with radiographic images and a necropsy. Our findings support the importance of consistent nesting activity and nest monitoring efforts in the country as a basis for conservation efforts.

Social consequences of energetically costly nest construction in a facultatively social bee.

Social groups form when the costs of breeding independently exceed fitness costs imposed by group living. The costs of independent breeding can often be energetic, especially for animals performing expensive behaviours, such as nest construction. To test the hypothesis that nesting costs can drive sociality by disincentivizing independent nest founding, we measured the energetics of nest construction and inheritance in a facultatively social carpenter bee (Xylocopa sonorina Smith), which bores tunnel nests in wood. We measured metabolic rates of bees excavating wood and used computerized tomography images of nesting logs to measure excavation volumes. From these data, we demonstrate costly energetic investments in nest excavation of a minimum 4.3 kJ per offspring provisioned, an expense equivalent to nearly 7 h of flight. This high, potentially prohibitive cost of nest founding may explain why females compete for existing nests rather than constructing new ones, often leading to the formation of social groups. Further, we found that nest inheritors varied considerably in their investment in nest renovation, with costs ranging more than 12-fold (from 7.08 to 89.1 kJ energy), probably reflecting differences in inherited nest quality. On average, renovation costs were lower than estimated new nest construction costs, with some nests providing major savings. These results suggest that females may join social groups to avoid steep energetic costs, but that the benefits of this strategy are not experienced equally.

Physico-chemical characteristics of honey produced by stingless bees (Meliponula beccarii) from West Showa zone of Oromia Region, Ethiopia

The study was investigated to characterize the physico-chemical properties of honey produced from stingless bees (Meliponula beccarii) in Oromia Region of Ethiopia. Honey samples were collected from underground soils through an excavation of natural nests from four representative districts (Wolmera, Jeldu, Toke Kutaye and Chalyia). About 120 honey samples (0.35–1.5 lit volumes) were collected and pooled for each respective area (district) for analysis. Principal component analysis (PCA) of pollen data and GPS were used to categorize the botanical origin and geographical location of honey sample sources, respectively. Consecutively, the physico-chemical characters were evaluated for the moisture content (MC), electrical conductivity (EC), pH, ash, total acidity (TA), hydroxyl methyl furfuraldhyde (HMF), insoluble materials (IM), and proline. The study results showed that the mean values of parameters for honey samples were: MC (29 ± 1.45), EC (0.22 ± 0.03), pH (3.73 ± 0.13), Ash (0.41 ± 1.1), TA (7.3 ± 0.36), HMF (18 ± 3.45), IM (0.70 ± 0.3) and proline (214.5 ± 15). There was no mean significance differences (P > 0.05) observed among the sampled districts for the analyzed parameters, except for proline. The values were compared against the standard physico-chemical parameters of Apis mellifera honey of Ethiopia and these values significantly varied for moisture content, total acidity and HMF. This is the first study investigated on composition property of stingless bee honey in Ethiopia and recall for further study on its nutritional and medicinal values so as to create a specific standardization.

Behavioral Rules for Soil Excavation by Colony Founders and Workers in Termites

Abstract Social insects produce complex nest structures as a result of the repetition of simple behaviors by many individuals. Individual actions are often consistent across different socio-environmental conditions, which enables colonies to build a variety of structures with minimal change in behavior. In this study, we show that the individual building behavior of termites can be a species-specific trait shared even between distinct morphological castes. Subterranean termites engage in soil excavation in two different contexts in their life history: foraging for resources by workers and initial nest excavation by colony foundation pairs. Our comparison of tunneling behaviors by colony founders of three different species revealed distinct transporting mechanisms; Heterotermes aureus (Snyder) (Isoptera: Rhinotermitidae) and Gnathamitermes perplexus (Banks) (Isoptera: Termitidae) carry sand particles using only their mandibles, while Paraneotermes simplicicornis (Banks) (Isoptera: Kalotermitidae) use their legs to kick sand particles backward. The observed behaviors are consistent with those of workers in each species, despite a substantial dimorphism of body size, especially in G. perplexus. Furthermore, the behavioral difference is associated with distinct tunnel development and task allocation patterns among species. Our study suggests that the nest building behavior of termites varies little with context or function within a species but can change among species, emphasizing the fruitfulness of comparative studies in future research.

Effects of nest building by the dominant hunting ant, Ectatomma sp. 2 (E. ruidum complex), on Andean coffee plantations

Soil removal by ants when building or adapting their nests generates ecological changes within the soil and on its surface, impacting both soil physical properties and plant growth. Ectatomma sp. 2 (E. ruidum complex) is a dominant hunting ant in numerous neotropical agricultural systems; however, its bioturbation impact on agroecosystems of economic importance, such as coffee, has not been studied. We evaluated it on coffee seedlings in Andean plantations of Colombia. Sixty colonies of this ant (30 in sun coffee, 30 in shaded coffee) were added within enclosed experimental units (EUs) containing coffee seedlings, and compared with their respective controls without ants. On average, dry soil removal by colony was 104.4 g during the two months experimental period (1.6 g day−1 colony−1), 13 times higher than in controls. A conservative estimate of their global bioturbation impact was calculated at between 59.3 and 203.1 kg dry soil ha−1, considering only two months of digging activity year−1 colony−1, a likely underestimation of the actual digging activity of this species. Positive effects of the presence of ants were found on several plant growth variables and on soil microporosity in shaded coffee plantations. Taking into consideration only the 14 colonies that were fully active until the end of the experiment, dry soil removal was on average 228.8 g (3.5 g day−1 colony−1) during the two months experimental period and coffee seedling growth in these EUs was significantly higher than in controls, indicating that, at the global scale, our bioturbation estimate could be higher under less restricted natural conditions and higher nest densities as found in other regions. Ectatomma ruidum sp. 2 appears as a functional agent in agroecosystems due to its ubiquity and its high bioturbation impact during the nest excavation period of activity, providing support services in agroecosystems and neotropical natural systems.

Behavior in Transition: Recovery of Behavior by an Obligate Parasitic Ant (Formica subintegra) Following Host Removal

Dulosis is a type of social parasitism in which a parasitic ant has become dependent on captured workers (hosts) of a closely related species. Dulosis can be either facultative or obligate depending on the degree of dependence on host workers. As parasites become more specialized over evolutionary time, their domestic abilities degenerate until they become unable to survive without the host. However, depending on the degree of specialization, the “lost” behaviors may display some degree of recovery when host workers are unavailable to do the tasks. The 12 species of the Formica sanguinea group are all traditionally considered to be facultative parasites. However, recent studies suggest that one member of the group, F. subintegra, has characteristics that are more consistent with obligate parasitism. To explore the degree to which F. subintegra has become obligate, this study examined the degree of recovery of foraging and nest excavation behaviors of parasites when hosts are removed. When parasites were isolated from hosts, they spent more time foraging and feeding regurgitated food to nestmates (oral trophallaxis), and tended to begin feeding sooner following a period of fasting than when hosts were present. Isolated parasites were able to excavate suitable tunnels and engaged in nest building behavior significantly more often than parasites in groups with hosts. These results indicate that F. subintegra demonstrates some recovery of its foraging and nest excavation abilities, and can be considered a less specialized (more primitive) obligate parasite. Formica subintegra and its facultative relatives can be used as models for studying the progression of dulotic evolution within a closely related group of social parasites, and may shed light on which factors contribute to the transition from facultative to obligate parasitism.

Welcome to the Atta world: A framework for understanding the effects of leaf‐cutter ants on ecosystem functions

Abstract Leaf‐cutter ants are a prominent feature in Neotropical ecosystems, but a comprehensive assessment of their effects on ecosystem functions is lacking. We reviewed the literature and used our own recent findings to identify knowledge gaps and develop a framework to quantify the effects of leaf‐cutter ants on ecosystem processes. Leaf‐cutter ants disturb the soil structure during nest excavation changing soil aeration and temperature. They mix relatively nutrient‐poor soil from deeper layers with the upper organic‐rich layers increasing the heterogeneity of carbon and nutrients within nest soils. Leaf‐cutter ants account for about 25% of all herbivory in Neotropical forest ecosystems, moving 10%–15% of leaves in their foraging range to their nests. Fungal symbionts transform the fresh, nutrient‐rich vegetative material to produce hyphal nodules to feed the ants. Organic material from roots and arbuscular mycorrhizal fungi enhances carbon and nutrient turnover in nest soils and creates biogeochemical hot spots. Breakdown of organic matter, microbial and ant respiration, and nest waste material decomposition result in increased CO2, CH4, and N2O production, but the build‐up of gases and heat within the nest is mitigated by the tunnel network ventilation system. Nest ventilation dynamics are challenging to measure without bias, and improved sensor systems would likely solve this problem. Canopy gaps above leaf‐cutter ant nests change the light, wind and temperature regimes, which affects ecosystem processes. Nests differ in density and size depending on colony age, forest type and disturbance level and change over time resulting in spatial and temporal changes of ecosystem processes. These characteristics remain a challenge to evaluate rapidly and non‐destructively. Addressing the knowledge gaps identified in this synthesis will bring insights into physical and biological processes driving biogeochemical cycles at the nest and ecosystem scale and will improve our understanding of ecosystem biogeochemical heterogeneity and larger scale ecological phenomena. A plain language summary is available for this article.

Ants know the secret to avoiding traffic jams

In a confined environment, ants divide labor to optimize nest excavation.

Evidence for atypical nest overwintering by hatchling lizards, Heloderma suspectum.

The timing of reproductive events (e.g. oviposition and hatching) to coincide with favourable seasonal conditions is critical for successful reproduction. However, developmental time may not match the duration between the optimal time for oviposition and the optimal time for hatchling survival. Thus, strategies that alter the time between oviposition and hatchling emergence can be highly advantageous. Arrested development and the resulting extension of the duration between oviposition and hatching has been widely documented across oviparous amniotes, but nest overwintering by hatchlings has only been documented in aquatic chelonians that live where winters are quite cold. Herein, we present a compilation of evidence regarding reproductive phenology by hatchlings of the Gila monster (Heloderma suspectum), a lizard inhabiting the Sonoran Desert of North America. Our data demonstrate that (i) Gila monster hatchlings from eggs oviposited in July do not emerge from their nests until late spring or summer of the following year, yet (ii) Gila monster eggs artificially incubated at field-relevant temperatures hatch in 4-5 months. Furthermore, we describe a fortuitous excavation of a hatching Gila monster nest in late October, which coincides with the artificial incubation results. Together, these results provide strong support for the existence of overwintering in the nest by a lizard, and suggest that this reproductive strategy should be explored in a broader array of taxa.